Eldritch_Lord
Adventurer
4E's Recharge powers are the closest analog I can see to the "You must wait 5 rounds before you use this power again" mechanic of most of the Vestige powers in Tome of Magic.
*rushes to read the grouped vestiges*
Also, a recharge is the closest thing we have to an "in-between" power. If it's too good to be usable every round, but not good enough to be restricted to 1/encounter, make it a recharge. There are effectively 5 levels of recharge to fine-tune balance.
And it's new, and different, and nothing else uses it yet. Isn't that good enough for you?

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lordkiwi: great work on Andras. I have a bunch of other D&D projects occupying my time (memo to self: finish up the incarnum conversion tonight) but I'll try to work in a vestige or two by the end of the week.