Pillar Analysis: Unique Effect (Mana Denial), Scarcity (Legends, Reserved List), Stax Archetype Staple
This nine-mana artifact costs X less to cast, where X is the greatest power among creatures you control, and it can cost as little as two mana
His Second Wind ability says Whenever an opposing character is damaged, you may ready this character
Inefficient, but if you cant afford the good tutors or can and are using busted black fast mana in your cEDH K'rrik, Son of Yawgmoth monster, Dimir House Guard does the work
Legendary Creature - Vampire Assassin Etrata, the Silencer Etrata can't be blocked
Im already interested in a 4-drop mana dork that gives me two mana, so being able to copy an X spell each turn is well above what Id expect to get out of it