I like the idea of the Runestones, from Cannith Crafting. Their cooldown is extremely long, which makes them not much use.

How about adding more runestones (at least type one for each essence type, currently only three)?
Change the cooldowns so they aren't shared, or are a lot faster.

Ideas for the other essence types:
Air - Knockdown and Slow,
Evil - Fear (maybe Phantasmal Killer at higher levels),
Fire - ongoing Fire damage,
Good - Healing over time (use on allies, not enemies),
Chaos - random effect (like Shiradi),
Mind - Charm,
Law - Banish?
Body - ?
Water - Freeze

Geoff.