Silver Myr

Oaken Siren

Flying, vigilance
{T}: Add {U}. Spend this mana only to cast an artifact spell or activate an ability of an artifact source.

Vedalken Engineer

{T}: Add two mana of any one color. Spend this mana only to cast artifact spells or activate abilities of artifacts.

Renowned Weaponsmith

{T}: Add {C}{C}. Spend this mana only to cast artifact spells or activate abilities of artifacts.
{U}, {T}: Search your library for a card named Heart-Piercer Bow or Vial of Dragonfire, reveal it, put it into your hand, then shuffle.

Hedron Crawler

{T}: Add {C}. ({C} represents colorless mana.)

Manakin

Iron Myr

Bronze Walrus

When Bronze Walrus enters the battlefield, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)
{T}: Add one mana of any color.

Apprentice Wizard

Ornithopter of Paradise

Kylox, Visionary Inventor

Menace, ward {2}, haste
Whenever Kylox, Visionary Inventor attacks, sacrifice any number of other creatures, then exile the top X cards of your library, where X is their total power. You may cast any number of instant and/or sorcery spells from among the exiled cards without paying their mana costs.

Automated Artificer

{T}: Add {C}. Spend this mana only to activate an ability or cast an artifact spell.