Fenrir can only be blocked by two or more creatures.

Whenever Fenrir deals combat damage to a player, you may pay the {3}{G}{G}. If you do, that player exiles the top three cards of their library. You may cast any number of nonland cards exiled this way without paying their mana costs.

At the beginning of your upkeep, you may reveal the top card of your library. If it's a creature card, put it onto the battlefield. If it's not, you lose life equal to its converted mana cost.

At the beginning of your upkeep, if you control Fenrir and have at least 10 cards exiled with Fenrir, you win the game.