Maelstrom Colossus

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Frogmite

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)

Myr Enforcer

Ornithopter

Myr Kinsmith

When Myr Kinsmith enters, you may search your library for a Myr card, reveal it, put it into your hand, then shuffle.

Darksteel Myr

Indestructible (Damage and effects that say "destroy" don't destroy this creature. If its toughness is 0 or less, it's still put into its owner's graveyard.)

Shield-Wall Sentinel

Defender
When Shield-Wall Sentinel enters, you may search your library for a creature card with defender, reveal it, put it into your hand, then shuffle.

Myr Retriever

When Myr Retriever dies, return another target artifact card from your graveyard to your hand.