Anyone have any advice on how to use this?
Heart's Desire + Twisted Wish could really foul up an enemy's day. The problem is figuring out what, exactly, "twisting" a wish really entails.
I've also heavily invested in primarily Evocation/Fire spells (for obvious reasons) along with a number of utility spells (some of which are also fire based, like Tar Pit and Scorching Ash Form).
Notably the other players don't seem to understand the concept of "I wish that guy was on fire" given the previous campaign (5th level: mage's tattoo + [wish verbal component] + scorching ray = 8d6) even after numerous statements of "the only wish you need to ask for is, 'I wish that guy was on fire.'" At 13th level setting people on fire is so much better (Elemental Blast bloodline power hits for 21d6 with a DC equal to a 9th level spell cast by the character, Chains of Fire, Contagious Flame, Fire Snake, Wall of Fire, Detonate...Damnation Stride...).
But the only thing I can't...quite...get a finger on is Twisted Wish. There's little reason to twist my allies wishes and enemies are hard to predict.