"If the worst parts of history can repeat themselves, it stands to reason that the best parts can as well."
—Teferi

Relic of Legends

{T}: Add one mana of any color.
Tap an untapped legendary creature you control: Add one mana of any color.

The List

Dominaria United

You can tap any untapped legendary creature you control, including one you haven’t controlled continuously since the beginning of your most recent turn, to pay the cost of Relic of Legends’s activated ability.