Any spell that has ''artifact'' in the type. It does not count if you cast a card with semblance anvil discount. Also, you get the discount if you exiled a card that shares a type with it.
June 26, 2011 7:58 p.m.
Lands are not spells.
Anything else is, at least for a time, a spell. When you cast any spell with the type "artifact" listed on the card (exceptions are the artifact lands from Mirrodin), Myrsmith can be activated.
June 26, 2011 11:21 p.m.
Also, casting at an altered or alternative cost is still casting.
June 26, 2011 11:23 p.m.
@xo2 why would the discount from the anvil stop an artifact spell from triggering Myrsmith ?
if you use an artifact for the anvil all artifacts cost 2 less to cast and even if you cast an artifact for 0 you can pay 1 with Myrsmith to put a myr onto the battlefield