User blog comment:GreenMoriyama/Judaeth, Messenger of the Limbo/@comment-1330314-20160729133913/@comment-1330314-20160904012935

If you want to avoid going full Limbo, there are a few other ways you could do this: for example, you could make the Infinite Limbo a completely separate plane, and have all units transported shift to a replica of the map, which would carry its own interesting double-edged effects (invisibility and untargetability from enemies on the physical plane, but also an inability to see or target them, for example). Alternatively, if you want to keep the Limbo as more of a persistent effect within the same map, perhaps you could have it apply one or a small set of buffs/debuffs, but those effects would have to be completely unique from any other champion's effects. There are several champions who offer protection, healing and movement speed buffs, and you can't really bank on your champion just being able to offer all of them in smaller amounts.

You're also right than an AoE effect with a diminishing radius over time could be interesting, though it would likely not be able to be control-focused. A diminishing radius means the ability is most powerful the moment it's cast, so ideally what you'd want is to use it for clutch, reactive plays, e.g. saving an ally or initiating combat, and over time you'd get diminishing returns from that. What you could also do is add some degree of increasing threat as the AoE reduces its size, down to a really powerful final moment at its end: for example, instead of having Destructive Cataclysm apply damage and a stun at the beginning of its cast, you could have it apply a more powerful effect once the AoE ends to all enemies still inside.