Each legendary creature you control gets +1/+1 for each other legendary creature you control.

{X}, {T}: Look at the top X cards of your library. You may reveal a legendary creature card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

"Tarnished Warrior. Spurned by the grace of gold. Be assured, the Elden Ring resteth close at hand"

—Godfrey, the First Elden Lord