The Gitrog Sovereign

Frogspawn - Whenever a Frog enters the battlefield under your control, create a 1/1 green
Frog creature token.
Royal Croak - At the beginning of your end step,
if you control five or more Frogs, you may search
your library for a Frog card and put it onto the battlefield tapped.
The Gitrog Sovereign reigns supreme, the grand
conductor of a watery orchestra.