Start small

As you pull yourself off of Thalinya's defiled form, you notice the Purestone, well, the twisted version of itself, lying on the floor of the hall. Darkness has consumed light again, and, with the power of Thalinya's sword within it, its energy has grown powerful.

"It seems the Purestone will absorb light and the energy of good and twist it to fuel its own power..." you muse.

Thalinya has picked herself up and wraps her tail around your waist. "The Stone will do as it always has: absorb its antithesis and warp it into its own form. What once would have cured most evils will now taint most good."

"That will be most useful," you grin evilly, reaching back to squeeze Thalinya's juicy, crimson ass.

"Who shall we convert first, master?" Thalinya asks, squeezing your balls.

"Hmm, We must separate them first. Their numbers could prove difficult until we can bolster ours and boost the stone's energy. I would love to see what kind of succubus that morsel Kaylee will make..."