Tahngarth, First Mate can't be blocked by more than one creature.

Whenever an opponent attacks with one or more creatures, if Tahngarth is tapped, you may have that opponent gain control of Tahngarth until end of combat. If you do, choose a player or planeswalker that opponent is attacking. Tahngarth is attacking that player or planeswalker.

Look at the top three cards of target opponent's library, then put them back in any order. That player looks at the top three cards of your library, then puts them back in any order.