(09:33:29 PM) Khaless Hetslen: Hmm... as a former DM, I'd start with something simple, like a dark bolt. A flat 1d6 with no modifiers to damage but +Wits to hit and build off there. For example a higher tier would be either plague aura which debuffs enemy living and buffs friendly undead or a necrotic life-drain blast. Each one using a pool. Lets say... 5 soul shard charges, one dark bolt means 1 charge used, gaining a spent charge on a flat 11-12. Toggling the aura would cost 3 charges, the blast would cost 2 or 3. (09:36:13 PM) Khaless Hetslen: Perhaps have certain perks, the charges work along the exact same lines as Holds but get refreshed sooner and more often. Could branch into minionmancer or prophet of death sort of archetypes.
(Almost) Everything tam suggests here:
And from Zee:
From Antithesis;
From OK: