Jinxy Rattrider

Sacrifice a Rat: Add {b}. Spend this only to cast
Rat spells or activate abilities of Rats.
Whenever another Rat enters the battlefield
under your control, you may pay 2 life. If you
do, search your library for a Rat creature card,
put it into your graveyard, then shuffle your
library.
{x}{x}, {t}, pay X life: Put X Rats from your
graveyard onto the battlefield.