that's all in the moles'dungeon (the first one is the slime pet when large though, feed it more).
if you don't know about the dungeon, this is from the guide:
"If you remember, in “the seed gathering run”, a horse marked your sweet fluffy wolf ass with a hoof… the next time you see Horace outside of the tavern (so only during the day), he’ll be convinced that horse is the being he was looking for, and pretty much drag you to it, but he can’t get through the barrier before the mountains (you resisting or giving in doesn’t really matter).
Go ask Jørgen (in his bar) about the horse, he is willing to give her to you, but only after the elections, which means you need to wait 3 days, then show up outside of Einar’s house or in front of the elevator in daytime to go on."
Basically, speak to Horace, then Jørgen, wait 3 days and do the quest that triggers.
the dungeon starts the moment you collect the last vote of this quest and enter einar's house again, so set your stats and buy the stuff you need before that (weapon enchantment is whatever, fire is decent), more details in my guide, both for the quests ("Guden's election day" and "the great molescape") and the gallery way below if you don't find everything.