Shimmer Myr
Mirrodin Besieged — rare
Artifact Creature — Myr
Shimmer Myr rulings:
2020-11-10: Once you announce that you're casting a spell, players can't attempt to remove Shimmer Myr from the battlefield to make that casting illegal. Removing Shimmer My after you've cast a spell won't affect that spell.
2020-11-10: Shimmer Myr has no effect on artifact lands because they aren't cast as spells.