If you manage to get Flotsom, Ursula's Spy out as well, you'll have a strong Evasive combo that will be hard for your opponent to deal with
That ability is "When you move your venture marker into this room, [effect]." After you move your venture marker into the last room of a dungeon and that room's ability resolves (or otherwise leaves the stack), the dungeon leaves the game and you have now completed it
The adventure portion, Alter Fate, doesn't bring a creature back directly to the battlefield, but the hand is good enough for two mana - Especially when you consider that you have access to a 2/2 with flying after you've cast it
Before we begin, it should be noted that we will specifically be discussing cards within the 99 of Demon-tribal decks, not Demon-tribal commanders themselves
Unless you specifically collect vintage cards, reprints offer better value