This is such a weird IP to pick, and an even weirder choice of killer. It feels really weird to cram a lich-turned-god into the same gameplay mechanics as a slasher movie killer, esspecially over many more iconic, recognizable, and unique character/monster designs.
I'm not a D&D fan in the slightest, but I would have thought something like a Mindflayer or some sort of lesser beholder would be more fitting, more inconic to D&D and more distinct from the other DBD killers.
On the D&D side, the final big adventure is releasing for D&D now before they refresh the rules starting in autumn. That adventure is high level and the main antagonist is Vecna, with him effectively having lieutenants of many of the other popular villains.
This isn't just a D&D tie in, it's an ad for Vecna: Eve of Ruin.
I just used those two because I figured they'd want iconic D&D monsters, whereas Vecna, esspecially after taking away the godhood and magic elements, is just a fairly generic undead skeleton.