Conjuro
Regresa hasta una carta de criatura objetivo de tu cementerio a tu mano. Crea una ficha de criatura Mercenario roja 1/1 con "

: La criatura objetivo que controlas obtiene +1/+0 hasta el final del turno. Activa esto solo como un conjuro".
You don't have to choose a target for Mourner's Surprise. However, if you do, and that creature card is an illegal target at the time Mourner's Surprise tries to resolve, it won't resolve and none of its effects will happen. You won't create a Mercenary token.