The Eye of Sauron

The Eye of Sauron costs {2} less to cast for each
Ring Wraith creature you control.
{t}: Tap target creature. It doesn't untap for as
long as the Eye of Sauron remains tapped.
{2}{b/r}{b/r}: Tap a Ring Wraith creature you control.
Create a fellbeast creature token. You may
activate this ability only once each turn.