i have solo’ed this dungeon on both mythic and heroic a couple times - the slime serpent never shows up.
UPDATE: i needed to do a full reset. now it works - problem solved.
As far as I know - it is 100% guaranteed.
Is it meant to be guaranteed?
For what it’s worth, Wowhead comments make no mention of the serpent being bugged. That’s usually the first place I go if I encounter something unexpected to see if anyone else has encountered it, but there isn’t really anything in this case. Gives me the impression that everything’s working as it should be.
Just a question, have you been killing the first two bosses or just skipping them?
Blizzard made a change during Shadowlands that you had to kill the first two bosses in Plaguefall as well for the Slime Serpent.
Youtube video comments had a bunch of people complaining of the same thing, one guy said to make sure you reset instances each time before going in and it fixes the problem.
I’d believe it was borked.
This mount was always super-easy to get, you just clear the dungeon and come back to the slime pool, and he’s there waiting.
So, if that’s not happening- yeah lol, it’s bugged.
Got this during Shadowlands, but I was curious, so I decided to test it.
Went in on an alt that’s never done Plaguefall. Heroic difficulty, all bosses killed. Nothing. Ran out, reset, tried again. Still nothing.
Definitely borked.
IIRC you cannot even get to the last boss without now defeating the first bosses.
And just to be sure OP, you are going in 100% solo right?