Yratest, Siren of Souls

When Yratest, Siren of Souls enters the battlefield gain control of target creature with power 3 or less for as long as Yratest, Siren of Souls is on the battlefield.
When Yratest, Siren of Souls dies gain control of target creature with power 4 or more for as long as Yratest, Siren of Souls is not on the battlefield.
"All you need is to believe is yourself and me. That is the only faith you'll ever need."