Since I am now writing Psionics of Lore, I realize that the Psionicist variant for the Sorcerer in my Heroes of Lore book has no real place any longer. It is fine if you want to have psionics play a minor role in your game world, but I feel like I am kind of cheating you out of a variant.
So to make it up to you, I decided to make a new variant to replace the Psionicist, and it's a relic from AD&D 2nd edition: the Wild Mage.
I mostly did it in honor of the release of Baldur's Gate: Enhanced Edition, which features a brand new Wild Mage character.
Wild Mages tap in to pure, unbridled and primal magic. Far beyond the energy of elemental magic, wild magic is unstable, chaotic and random as it lies in its constant state of imbalance. Wild Mages try to harness this chaos, usually leading them to be quite strange and random in personality.
Wild Mages get one less spell per level. Instead, they can tap into the primal wild magic three times a day. When they access wild magic, they choose a spell and then roll a d20. The result of the roll determines at what effective level the spell was cast. For example, if a 5th level Wild Mage casts a spell and rolled a 20, the Wild Mage would effectively be considered level 7 for purposes of determining spell effects and damage. The table below details the level modification
The drawback to this is that every time a Wild Mage uses one of her taps, she must make a Will save. If she fails, she must roll on the Wild Magic table, located on p. 21 of the Treasure Keeper's Tome.