DURIN VII LORE
They say also that the Seven Fathers of the Dwarves return to live again in their own kin and to bear once more their ancient names: of whom Durin was the most renowned in after ages, father of that kindred most friendly to the Elves, whose mansions were at Khazad-dûm.
For the Dwarves asserted that the spirits of the Seven Fathers of their races were from time to time reborn in their kindreds. This was notably the case in the race of the Longbeards whose ultimate forefather was called Durin, a name which was taken at intervals by one of his descendants, but by no others but those in a direct line of descent from Durin I. Durin I, eldest of the Fathers, 'awoke' far back in the First Age (it is supposed, soon after the awakening of Men), but in the Second Age several other Durins had appeared as Kings of the Longbeards (Anfangrim). In the Third Age Durin VI was slain by a Balrog in 1980.
There [Durin I] lived so long that he was known far and wide as Durin the Deathless. Yet in the end he died before the Elder Days had passed, and his tomb was in Khazad-dûm; but his line never failed, and five times an heir was born in his House so like to his Forefather that he received the name of Durin. He was indeed held by the Dwarves to be the Deathless that returned; for they have many strange tales and beliefs concerning themselves and their fate in the world.
It was prophesied (by the Dwarves), when Dain Ironfoot took the kingship in
Third Age 2941 (after the Battle of Five Armies), that in his
direct line there would one day appear a Durin VII - but he
would be the last. Of these Durins the Dwarves reported that
they retained memory of their former lives as Kings, as real, and
yet naturally as incomplete, as if they had been consecutive
years of life in one person.
And the line of Dain prospered, and the wealth and renown
of the kingship was renewed, until there arose again for the
last time an heir of that House that bore the name of Durin,
and he returned to Moria; and there was light again in deep
places, and the ringing of hammers and the harping of harps,
until the world grew old and the Dwarves failed and the days
of Durin's race were ended.
Thus it was here that 'Durin the Last' emerged, and it is said of him
that he returned from Erebor to Moria and re-established it.
PREMISES
I just found these paragraphs from Hystory of middle earth. Which are probably the most detailed ones. I also inserted the family tree of Durin's line.
The lore in this case in not so reach, but most of the main elements have been used to create our personal storyline (see next spoiler: Durin VII timeline and story).
We are sure that the birthday of Durin VII was prophesied during BOTFA (2941 TA). He will be the last one and he will reclaim the fallen realm of Moria.
The precise date of birth is not mentioned, neither if he's the son of Thorin III.
Anyway we cannot exclude the fact that he was born already during the war of the ring. Being him the true heir of Durin, he can probably live longer (thousands years) and longer with respect to the normal dwarfs (some centuries): a sufficiently large age to rule during the Fourth Age and see the end of Durin's folk.
Following all these premises, we have crafted a new story without exiting from the edges of lore, and connecting this with the heart of the whole concept: the theme refusal of the ring and the last reincarnation of Durin (see the last spoiler: Durin VII Ring mechanic and Concept).
HANNAR THE HAMMER OF EREBOR (TA 2965 -...FA)
Hannar, the skilled or the Hammer, was born to Thorin III Stonehelm on 2965 of the Third Age. Hannar grew and was trained to become a mighty warrior—his name was selected for his unique proclivity towards working metals and other forgings. Many Dwarfs felt this was a unique gift to acquire at such a young age, and rumors begin to thrive that Durin’s hand was upon the young dwarf. Eventually Hannar became a master smith, able to work the most precious jewels and hew great weapons of metal and Mithril. (Young Hannar)
By age 36, Hannar had risen through the ranks as an incredulous warrior—able to wield a hammer or axe superior to any dwarf in Erebor. Such was his skill and master of the Dwarvish arts, that his grandfather, King Dain II Ironfoot asked him to accompany the revered hero Bilbo Baggins to Erebor. Gathered together with Nar, and Anar—Hannar physically escorted Bilbo to Imladris in 3001 TA. There, Hannar and his warriors departed back to Erebor. Hannar had accomplished his first mission and a celebration was held. This was considered very rare for a Dwarf of Hannar’s age as he was the youngest of the three Dwarfs and it was said that Dwarfs were not ready for such burden till the age of 40, but seeing Hannar excel as he once did, King Dain II had great faith in his grandson and knew he could accomplish much.
(Hannar the Skilled Blacksmith)
Several years later, Hannar would see his grandfather reject the offer of Sauron’s messenger for Durin’s ring in 3018. In 3019 at age 54, Hannar participated in the Battle of Dale where his grandfather King Dain II fell in battle fighting over the body of King Brand. Hannar fought with the heroes of Erebor and his father Thorin III. Eventually, the Easterling hoard was broken and Erebor was victorious following the One Ring’s destruction and Sauron’s departure from middle earth. (The Battle of Dale)
Thorin III became king of Erebor and ruled justly in his father’s stead for many years. During his rule, Thorin saw Gimli become Lord of the Glittering Caves and sought to recolonize Moria. Over time, Thorin III grew old and while his son Hannar fought in Moria. (The Last Battle to reclaim Khazad-dûm)
While fighting against the Goblins of Moria, Hannar began to recognize many stone monuments and structures. Hannar fought his way through hordes of Goblins and slew everything that stood before him. Seeing himself fulfilling the legends of old, Hannar proclaimed himself Durin VII at age 176 (120 of the Fourth Age). At age 230 (174 FA) Moria had been reclaimed and Thorin III departed from the world—Durin VII, (envisioning and bearing the spirits of the Durin’s before him) ruled with longevity in his father’s stead deep into the Fourth Age.
Eventually the Dwarfs disappeared into their halls of stone. Durin VII and the Dwarfs passed from middle earth, but left a host of legends that would carry on throughout time as well as the tales of the descendant of Thorin III, Hannar the last king of the Dwarfs.
(Durin VII the Last)
Sources:http://tolkiengateway.net/wiki/Durin_VIIhttp://tolkiengateway.net/wiki/Thorin_Stonehelmhttp://tolkiengateway.net/wiki/D%C3%A1in_Ironfoothttp://tolkiengateway.net/wiki/Bilbo_Bagginshttp://tolkiengateway.net/wiki/HannarHere there's a list of old norse dwarves names, from which Tolkien himself taken the majority of the dwarven names, you will surely recognize many other names together with Hanarr (Hannar) (examples: Gandalfr-->Gandalf, Yngvi-->Ingwe):
https://is.cuni.cz/studium/predmety/index.php?do=download&did=67368&kod=ARL100258DURIN VII IN GAME
Ring mechanic: the theme of refusal
Then about a year ago a messenger came to Dàin, but not
from Moria – from Mordor: a horseman in the night, who
called Dàin to his gate. The Lord Sauron the Great, so he
said, wished for our friendship. Rings he would give for it,
such as he gave of old. And he asked urgently concerning
hobbits, of what kind they were, and where they dwelt. ‘‘For
Sauron knows,’’ said he, ‘‘that one of these was known to
you on a time.’’
At this we were greatly troubled, and we gave no answer.
And then his fell voice was lowered, and he would have
sweetened it if he could. ‘‘As a small token only of your
friendship Sauron asks this,’’ he said: ‘‘that you should find
this thief,’’ such was his word, ‘‘and get from him, willing or
no, a little ring, the least of rings, that once he stole. It is but
a trifle that Sauron fancies, and an earnest of your good will.
Find it, and three rings that the Dwarf-sires possessed of old
shall be returned to you, and the realm of Moria shall be
yours for ever. Find only news of the thief, whether he still
lives and where, and you shall have great reward and lasting
friendship from the Lord. Refuse, and things will not seem
so well. Do you refuse?’’
At that his breath came like the hiss of snakes, and all who
stood by shuddered, but Dàin said: ‘‘I say neither yea nor
nay. I must consider this message and what it means under
its fair cloak.’’
‘‘Consider well, but not too long,’’ said he.
‘‘The time of my thought is my own to spend,’’ answered
Da´in.
‘‘For the present,’’ said he, and rode into the darkness.
Heavy have the hearts of our chieftains been since that
night. We needed not the fell voice of the messenger to warn
us that his words held both menace and deceit; for we knew
already that the power that has re-entered Mordor has not
changed, and ever it betrayed us of old. Twice the messenger
has returned, and has gone unanswered. The third and last
time, so he says, is soon to come, before the ending of the
year.
We decided to link King Dain with the theme of refusal of the ring: King Dain it is the oldest and so possibly the wisest king of the three realm in game. Furthermore,following the events of the book, he also refuses three ring of the dwarves offered by Sauron: this fact makes his character even more "evil resistance".
We discuss multiple times the double choice, because currently it is a unique future of Galadriel. As we have demostrated through the lore, the
refusal is the most canonical, and it would be very good and unique to have only this choice.
King Dain Ring Function: King Dain gives up the ring to his grandson, which he's recognized as the true reincarnation of Durin I. He's so the only one who can use it in a proper way, without being corrupted by its evil influence. With the one ring his spirit is further strengthen, awakening totally the original power of his ancestor.
The new hero of Erebor will be so only a
ring feature, freeing us of the burden of creating a new recruitable hero.
Durin VII is summoned directly near Dain, starting from level 1 and with the following values:
HP: 4500
Melee damage: 400
Once in game, will be characterized by two forms:
Durin's Heir: At the beginning of the game, Durin VII doesn't own the abilities of his forefather. To quickly recovers the ancient knowledge of Durin I, he need to complete some tasks. Given that Durin is an over-the-average hero in different aspects (even comparing him with other ring heroes), we deem a longer path towards power necessary in the name of balance. Furthermore, the
Rune system presented below also gives some more strategically interesting options to the player at the beginning.
Durin The Last: after the journey to Moria, Durin finally recoves all his ancient magnificence. All the past abilites (equal or very similar) are now available at different levels.
Concept and models
(Durin VII The Heir) (Durin VII The Last)
Durin's Heir
Level 1 Durin's Heir (passive): In order to prove himself as the true incarnation of Durin the Deathless the Heir needs to regain the memories of his forebearers, which will unravel his extraordinary powers. His remarkable endurance is an essential feat to his ascend, and allows him to reject death when he faces the end. When his healthbar is almost spent Durin becomes invulnerable for a time.
With no tasks completed he becomes invulnerable to any damage for about 5 seconds, with 1 completed for about 10 seconds, with 2 completed for about 15 seconds, and with all 3 completed for about 20 seconds. This ability and its effective duration is transferred to his next form.
Rune of Heroism: Studying the deeds of former kings and veterans Durin remembers their feats in battle and leadership. He leaves his personal runes on a Heroic Statue which encourages all friendly heroes on the map to recover faster. As long as the statue stands heroes earn experience faster and have their ability cooldowns reduced.
Rune of Adoration: The knowledge to the art of war is recovered by Durin as he inspects Dwarven warriors practice. He leaves his personal rune on a Dwarven Barracks or Siegeworks which provides a great boost in experience gain during the first 2 minutes of every unit leaving recruitment structures.
Rune of Protection: As the Heir ponders ways to improve Dwarven defenses he recollects the capacity of rendering stone less vulnerable to the elements. Applied to a Stoneworker, Mine or Lumbermill resource structures are globally more resistant to magic and elemental damage.
The three runes share a cooldown of 2-3 minutes that starts when the Heir is summoned. It involves a strategic decision which rune is chosen first, according to what aspect in the Dwarven army needs support. The runes are in effect until the target building is destroyed. In his next form Durin can no longer apply these runes,
so the targeted buildings need to be well protected or their effects will be of short duration. 
Level 1 Journey to Khazad-Dum (upgrade): Durin decides to journey to Khazad-Dum in order to conquer the lost kingdom and reclaim his heirlooms. He will return on Durin's Day.
The duration and cost of this journey are dependent on how many tasks have been completed before the Heir is sent away. Without any tasks completed it costs 1500 resources and takes 1 minute before he returns, with 1 task completed 1000 resources and 45 seconds, with 2 completed 500 resources and 30 seconds, and with all 3 completed 0 resources and 15 seconds. Including Durin's Day at his return is meant as an inventive way of bringing back the former weather Spell just once, and it warns the enemy of his arrival (just like Sauron's Darkness).
Indeed what I managed to present in this portrayal is that the player has the choice to either increase Durin's durability in the long term while supporting various aspects of his army, or get him ready for battle immediately with the risk of losing him prematurely as he did not fully regain his abilitities of legend.Durin The Last
"Heritage of the ancestor" (passive): Durin VII complete his path as true heir of Durin I during the travel to Moria. All the memories of his past life are now reemerged, and the great emptiness of Khazad Dùm is filled with new life. Durin VII gets +1000 HP and eventually finds the equipment of his forefather (change of the model from the first to the second showed above):
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"Axe of Durin": Durin the Last gains Aoe damage and knock back units thanks to the legendary axe of his forefather.
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"Crown of the seven stars": The legendary crown is recovered from Mirrormere. All Dwarven heroes near Durin VII are inspired and get +30% armor.
I simply deem this ability a good way to introduce the old equipment of Durin and to quote the travel written in the lore (and in our invented story). 
Level 1:"Durin The Last" (passive): Durin VII is the last King of the Dwarves and the true reincarnation of Durin I. He will lead his folk until the end of the Dwarven race will come. Durin escapes death for a certain time after his healthbar is spent.
This ability remains the same, but it is adapted for the new Durin 
.
This ability is carried over from its previous form with the according effect duration. 
Level 3: "Master of Defence": the ancient knowledge in stone mastery of the first forefather lives again through his heir: Durin VII use it to make the defences of the Dwarves indestructible. All the allied walls,towers,gates in the selected area (wide) will be significantly strengthen.
I change the ability as only defensive because it fits very well with the dwarves, and also it is not redundant with runes because it affects towers gates and walls. in light of the new siege overhaul I think it could be very useful and cool to have such a power . Make it also offensive like in the past I'm afraid it could be too much op, considering also the new balance that the 4.5 siege patch will bring (the old combo master of stone + earthquake was devastating ).
Level 7: "Word of Silence " : Durin VII speaks a word of silence that stops all fighting in a wide area for the benefit of nearby allies who are slowly healed. Enemies in the area are paralysed and enemy buildings do not function for a medium period of time.
Also very similar to the original one 
Level 10: "Fire of Aulë's forge" - Durin VII the Last calls the aid of the Maker Mahal. Aulë makes the ground of Middle-earth burst into flames by the fire of his forge. Deals medium damage in a wide area around Durin. The magic fire of Aulë damages the equipment of the enemy unit : survived units get a significant reduction of armor and damage.
I like a lot this last ability, and maybe the last King worth the intervention of Aulë, as a last act before the end of the world of the dwarves. I also make it special, relating the fire with weaponry, which is quite logical since it comes from a Forge (not a random forge but THE forge).
Following the evolution of the skillset, the player have a more defensive and funerable hero at the beginning, but he/she will be rewarded at the end with the complete power of Durin. Final comments on the concept
The palantir images of the abilities can vary, i chosen them because i deem them proper and good in my personal taste. Maybe some of them can be more so to say "general" with respect to mine. You can recognize the depiction of King Dain of Vanilla
. That picture give me the feeling of an "old king", in particular the shadow that cover half of the face of Dain, brings a feeling of "The Last one", something doomed to the end. Moreover, the crown is very similar to the one of the model.
Credits for the model of Durin's Heir goes to the Fourth Age mod, that is a archived mod here in MU (DVZ mod). The second model is a fusion of the first one + the armor of Durin the Deathless (i made the collage using GIMP to show how it looks). Since many members are very fond of it, and since it is complete Edain style (no movie inspiration) i decided to keep this unque piece of art. Below you can see the old model of Durin the deathless, if you like to compare the two:
Umfrage