I'm not so sure if it is a demonic altar in Kai's case because some of the other members also have stage names: Suho (Kim Junmyeon), Xiumin (Kim Minseok), Chen (Kim Jongdae). But it's interesting to note that these names were carefully picked by Lee Soo Man himself. Especially Kai's has a very specific meaning in relation to EXO's concept. Kai means"open" in Chinese, which makes sense since he has the power of teleportation. He has the important task of transporting the EXO members to different universes and he's the only one who can do so; they can't go anywhere without him.
But I'm not going to lie, the idea that it could be a demonic altar started playing in my mind after I saw him putting more and more emphasis on his stagename during his solo promotions. The line "please remember you're Kim Jongin too" kept crowding my mind while I was watching parts of his insta live. I'm scared that he'll eventually talk himself into a multiple personality disorder if it continues like this and it will make him easier to control if they plan on doing MK Ultra on him. He's a very deep thinker who's very aware of who he is as a person, although he doesn't really show it that often. So I sincerely hope that he will keep protecting his soul from evil.