Mind Stone

{3}{t}: Take control of target creature until
the end of your turn, untap that creature
{6}{t}: You may gain control of target creature for
as long as Mind Stone is tapped
{w}: Mind Stone does not untap during owner's
untap step
— "The jewel appears to be a protective housing for something inside, something powerful." "Like a
computer. What's it look like it's doing?" "Like it's thinking."