Buttercup, Provincial Princess - Sisay, Weatherlight Captain (SLD-1444) - Secret Lair Drop / Buttercup, Provincial Princess (Borderless) Foil

Sisay gets +1/+1 for each color among other legendary permanents you control.
: Search your library for a legendary permanent card with mana value less than Sisay's power, put that card onto the battlefield, then shuffle.