What CR would a lich Simulcarum be?

[stenver]

I have a lich who has made a Simulacrum of himself. He plans to send the Simulacrum to a critical quest location against the party - teleport in with some strong allies and rain wreck. Considering the party has already had quite a few fights today, they should be in for a nasty fight. I have no idea how to calculate the CR though. The spells and special abilities make it way too complicated.

So what CR would be Simulcarum be? To make it easier, let's say the Simulcarum doesn't have any legendary actions.

[Gastronomie]

TBH a majority of the Lich's powers come from its Rejuvenation ability (and Legendary actions). Without them, it's not much different from the CR 12 Archmage. It does have a higher spell DC and certain nasty spells, though, so I'd say CR 15 or perhaps 16-ish. Whatever seems to work.

And he needs minions to back him up, anyways. If you send just the Simulacrum, chances are he'd die within two or three rounds, having so low AC and HP.

[stenver]

Thanks. I was wondering how the CR difference can be so big, especially considering the low HP of the lich.

Yeah, he will have lot's of minions.
2 Custom skeleton mages(CR 1, up to level 3 spells)
4 skeletons(CR 1/4)
1 "white walker"(CR 4, basically a boosted wight immune to everything except Adamatinum weapons)
Finally this guy(CR 10): https://i.imgur.com/4ykIJtM.jpg