You can only use each effect of "Merlin" once per turn.

?You can Tribute this card; Special Summon 1 "Noble Knight" monster from your Deck. You cannot Special Summon monsters the turn you activate this effect, except "Noble Knight" monsters.

?During either player's turn: You can banish this card from your Graveyard; immediately after this effect resolves, Synchro Summon 1 "Noble Knight" Synchro Monster using monsters you control.

?During either player's turn: You can banish this card from your Graveyard; immediately after this effect resolves, Xyz Summon 1 "Noble Knight" Xyz Monster using monsters you control.