Strago and Relm
Sketch and Lore — , 
: Target opponent exiles cards from the top of their library until they exile an instant, sorcery, or creature card. You may cast that card without paying its mana cost. If you cast a creature spell this way, it gains haste and "At the beginning of the end step, sacrifice this creature." Activate only as a sorcery.
Illustrated by Darius Zablockis
This printing
Prices
If you cast a spell "without paying its mana cost," you can't choose to cast it for any alternative costs. You can, however, pay additional costs. If the spell has any mandatory additional costs, those must be paid to cast the spell.
You cast the card while Strago and Relm's ability is resolving and still on the stack. You can't wait to play it later in the turn. Timing restrictions based on its types are ignored.
If a spell has
in its mana cost, you must choose 0 as the value of X when playing it without paying its mana cost.
