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.
Legalitet:
Standard: Ej legal
Pioneer: Ej legal
Modern: Legal
Legacy: Legal
Vintage: Legal
EDH / Commander: Legal
Pauper: Ej legal
Explorer: Ej legal
Historic: Ej legal
Brawl: Ej legal
Premodern: Ej legal
93/94: Ej legal
Shimmer Myr är Legal i dessa block: Scars of Mirrodin