Cold Storage

{3}: Exile target creature you control.
Sacrifice this artifact: Return each creature card exiled with this artifact to the battlefield under your control.

Helm of Possession

You may choose not to untap this artifact during your untap step.
{2}, {T}, Sacrifice a creature: Gain control of target creature for as long as you control this artifact and this artifact remains tapped.

Empress Galina

{U}{U}, {T}: Gain control of target legendary permanent. (This effect lasts indefinitely.)