Excalibur

This spell costs {x} less to cast, where X is the total mana value of historic permanents you control. (Artifacts, legendaries, and Sagas are historic.)

Equipped creature gets +10/+0 and has vigilance.

Equip legendary creature {2}

"Sheathed in the breath of the planet, a torrent of shining life. Feel its wrath."
- Artoria Pendragon