Marvellous ideas! This thread is a real forge of fantastic concepts
Look, I'm literally torn inside between two major options. I haven't wrapped my head around a final solution yet. I hope we'll be able to call it a satisfying end, very soon. Before listing the two, I have taken the liberty to rule out the active/passive hypothesis, as it seems to me that it somehow halves the potential of the ability and separates aspects that should instead exist together (on equal terms).
1. Your previous idea is actually very revolutionary, and incredibly unique. A passive influence, therefore perpetual, would fit Vilya the best. Only, unfortunately, you've also identified the main implications which such rendition would cause:
- He would have two passive abilities in his skill set.
- The Ring of Air would inevitably end up being boring.
- There wouldn't be many grandiose graphical effects we could find (I infer that people would not like to have their own castle/camp permanently illuminated).
- All in all, it would not be appealing, to say the least.
2. The second option, mind, is probably the boldest one. Much bolder than inherently unique. Nonetheless, I'm sure it would fare overwhelmingly well; what players would fancy and appreciate a good deal. Hence, let us retrieve from the void a dismissed concept:
Vilya's Blessing: Vilya shields Rivendell from decay and evil. All Elven buildings, heroes and units will be blessed with temporary invincibility.
As you may see, nothing so intricate or complex. Just the past prowess of Nenya, albeit applied globally.
- This concept respects the definition of decay we had discussed together, granting full protection from enemy spells, hero abilities, attacks (all natures) and whatsoever hostile act. Ergo: immunity.
- The Ring would in this way be enormously satisfying to use. A worthy, decent, magnificent level-10 ability.
- As you may have noticed, only Elves are affected. Rangers, Hobbits, Elendil, Isildur (and so forth) are thereby excluded.
- Duration is the weak point of the situation. It necessarily has to remain short, for the sake of balance. 20 seconds, I suppose.
- Regardless of time, here is another utmost argument: Vilya would finally be the ruling Ring among the Three. The mightiest of the Three Rings, gifted with the strongest supportive feature in the whole game
By consequence, in light of Vilya and Wind Armour, Elrond's price should be reasonably raised to 3000 resources, which is the maximum value for a hero. If we consider that he's one of the wisest, most experienced characters in the lore, that would make for a stunning improvement. A landmark overhaul, to be sure.