The Grand Magister Rommath which I played, also casted cards from my opponent including Ghouls’ Night which caused lethal on me.
I think it might be related to the Psychic Scream card? Cause after that was played then it played ghouls night for my opponent
If a minion switches ownership during a battlecry then the battlecry resolves as if your opponent played this minion. So this is intended.
This happened to me as well, and I am certain that the results were a bug. After Psychic Scream, multiple spells, including Corpsicle and Ambush Predators, played as if my opponent had played them. This resulted in my opponent getting a 1/1 with poison on board and a new Corpsicle returned to her hand.
Did you not read what @Joachim wrote?
If a minion changes owners during a battlecry, the remaining battlecry effects belong to the new owner.
Psychic Scream shuffled Rommath into your opponent’s deck, thus changing his owner.
If your opponent steals your lifesteal minion, you don’t expect the lifesteal effect to heal you anymore, but to heal your opponent, right ?
Same thing with an ongoing battlecry
Oh, now I understand it. Thank you, my bad.