Lich's Mastery does not block lifegain

James13

I ran into this trying a "win with X or less" health battle in story mode.

My deck included Slimefoot (Dominaria), Tendershoot Dryad, and Lich's Mastery.

I hit a black activate gem off Slimefoot and gained life despite Lich's Mastery being in play.

Notes: My hand was full each time I gained life but I don't know if it was related.  Alhamarret's Archive was also in play.

https://imgur.com/a/Xbzbxtj

Szamsziel

Almanarch archive is the reason. Normal lifegain is blocked, but almanarch add the bonus not taking into account lich mastery.
Main question: "it's a bug or a feature?"