All-Blocker Mohngu

[Finora]

I attacked him once & got adds & died way faster than I could figure out what I was supposed to do to kill him.

Now everytime I go down to fight him he just kills my pet outright & becomes a greyed out broken encounter.

I am going nearer to the edge of his ledge now due to the other creatures (the ones that were adds the first time) but I can't think of any reason his encounter would break if I'm standing in an area he normally paths.