Just off that top of my head -

Anarchic Damage : You have felt the touch of Xoriat and the eternal Madness that dwells within; Now you can channel is lurking hunger towards your foes!
*I really wanted to see more use out of Xoriat-styled abilities, maybe even mesh with the Symbiont. Probably comes with a penalty to Will Saves* Chaotic only

Ice Damage : You wield the whirling fury of winter, having signed a pact with a fearsome scion from the plane of Risia, the endless frozen land.
*Could also be an Ice Devil like the one mentioned in Under the Big Top*

Lawful Damage : You devote yourself to the rigid order of Daanvi and attain an inner peace, with your newfound strength you can oppose great evil.
*Works as a counterpoint to Xoriat* Lawful only

If the Anarchic / Lawful setup is uninteresting, I also considered Mabar for "Negative" damage, and mesh with PM or Necro Cleric