Araña pescadora celeste

Notably, this means that players won't get to know what nonland permanent you plan to target before you choose whether to sacrifice a creature.

Skyfisher Spider's first triggered ability doesn't have any targets. If you choose to sacrifice another creature, a second triggered ability (called a "reflexive" triggered ability) goes on the stack and you choose a target nonland permanent at that time. Players may respond to that second ability as normal.