Tempered Steel

Artifact creatures you control get +2/+2.

Sphinx's Decree

Each opponent can't cast instant or sorcery spells during that player's next turn.

Counter target noncreature spell unless its controller pays {2}.

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{T}: Add {C}.

Other Myr creatures you control get +1/+1.
{1}, {T}: Untap each other Myr you control.

Return target creature to its owner's hand. Its controller loses 1 life.

{T}: Add {C}.
{2}, {T}: You gain 1 life for each colorless creature you control.

Spend only mana produced by creatures to cast this spell.

Whenever you cast an artifact spell, you may pay {1}. If you do, create a 1/1 colorless Myr artifact creature token.