Sothis, The Beginning

Bestow {1}{w}{u}{g}
Flash
{1}{g}{u}{w}: Return this creature and all auras
attached to it to it's owner's hand.
When Byleth, Mercenary Tutor would leave
the battlefield, you may sacrifice Sothis. If
you do, return Byleth, Mercenary Tutor to
the battlefield transformed under its owner's
control.
Partner with Byleth, Mercenary Tutor.