Fell Horseman

An effect may refer to a card, spell, or permanent that “has an Adventure.” This refers to a card, spell, or permanent that has an adventurer card’s set of alternative characteristics, even if they’re not being used and even if that card was never cast as an Adventure.

Fell Horseman will be put on the bottom of its owner's library only if it's still in the graveyard when its ability resolves. If it leaves the graveyard before that point, it will stay in whatever zone it's in, even if it's returned to the graveyard before the ability resolves.

If you cast an adventurer card as an Adventure, use only its alternative characteristics to determine whether it’s legal to cast that spell. For example, if you control Johann, Apprentice Sorcerer (“Once each turn, you may cast an instant or sorcery spell from the top of your library.”) and Questing Druid is on top of your library, you can cast Seek the Beast, but not Questing Druid.