Mordred, Throne Betrayer

Mordred, Throne Betrayer enters with two +1/+1 Counters
{x}:Target player exiles the top X cards
of their library. You may cast any number of
nonland cards with converted mana cost X or less
from among them without paying their mana costs.
You may only use this ability while it is your turn.
Remove a +1/+1 counter from Mordred, Throne Betrayer: add {1}, this mana can only be used for abilities of creatures