Beguiling Siren

When Beguiling Siren enters the battlefield, gain control of target creature until Beguiling Siren leaves the battlefield.
{3}{u}{b}, {t}: Search your library for a fish creature, reveal it, and put it into your hand. Shuffle your library.
Whenever a fish enters the battlefield under you control, put a stress counter on target creature you don't control.
"The aquatic devils have remade the poor girl in their image! She is their queen, and their slave!" — the Anc