Vilemaw

359.3.e.6. Instructions that can't be followed because of illegal targets, or because they reference information that is unavailable, are considered Ignored. Instructions that can't be followed for any other reason are Negated. Example: A player plays Ride the Wind choosing to move their unit at Vilemaw's Lair to base. Base is a legal move destination for Ride the Wind, but on resolution of Ride the Wind's effect, the move instruction will be negated because Vilemaw's restriction makes the instruction impossible. Example: A player plays Hidden Blade targeting a unit at a battlefield. In reaction to Hidden Blade, the unit's controller plays Flash, moving it to base. Hidden Blade's instruction "Kill a unit." will be ignored on resolution of the spell.

758.2.a. This will also occur if the Game Object is no longer among the set of objects that are made untargetable by a Game Effect. Example: Alpha Wildclaw and Vilemaw are controlled by the same player and located at a battlefield. An opponent targets Vilemaw with Rebuke. Before Rebuke resolves, Vilemaw's controller plays Discipline targeting Alpha Wildclaw, making Vilemaw no longer a legal target. Rebuke's controller then targets Alpha Wildclaw with Star-Crossed. When Star-Crossed resolves, Alpha Wildclaw's passive ability no longer applies to Vilemaw, making it a legal target for Rebuke. After all spells and abilities have resolved, both Vilemaw and Alpha Wildclaw will be returned to hand.