Using Spine of Ish Sah and mana generators like Caged Sun can ensure your opponents threats are under control
Gitaxian Probe Gitaxian Probe is banned in a lot of MTG formats, and for good reason
Abilities that trigger when a player casts a spell (like Mirrorwing Dragon's ability itself) won't trigger
Now make them a creature that green, a color that typically loves enhancing its own creatures, cant even touch themselves
Black's strengths are destroying creatures, forcing opponents to discard cards, making players lose life, and returning creatures from graveyards
Normally, I'd say that maybe this could be printed in a set focused in a format other than Standard, but delve has proven to be problematic in most larger formats