Does anyone know if the Raven Queen has stats, and if not, what would you suggest they be? (5E)

In my campaign the entire plot so far has been that the Raven Queen has gone mad from her time as a goddess, and has started throwing the world out of balance, or rather, all of them, though the players only actually participate in one. As a result, I intend for her to be the final boss, but I have absolutely no idea where to start with making her into an enemy. The players have Pelor on their side, as he is opposed to her maddening actions, but he won't directly fight her himself.

So... Anyone got any ideas? It's not for a while yet. I'm not opposed to minions, but they'd be other NPCs that sided with her instead of with Pelor during the campaign (or simply reincarnations of some of the NPCs the players have killed throughout the story). I'd like the fight to have at least two or three phases, and to be quite tough. Losing the fight is an option for an alternate ending as well, of course, but I'd like the fight to be winnable.

So yeah. Completely lost, and seeking some suggestions. The players will be about level 16 or so I would imagine, though I could bring them higher through more story content if need be.

Major things I'm looking for are HP, AC, abilities, damage, and gimmicks to the fight. The setting is going to be a seemingly endless darkness. A void, in which you cannot see the floor you walk on, but for all purposes it's going to be an open field, flat as can be. They will have a Paladin of Pelor there with them - a character buffed like mad to be on a near-god level themself, as Pelor pours his strength into them. Feel free to homebrew the crap out of this if you want, I just want it to be an exciting end to the game, hard as that may be. I just thought maybe it'd be fun to get the community in on this with me.