Rin and Seri, Inseparable

Whenever you cast a Dog spell, create a 1/1
green Cat creature token.
Whenever you cast a Cat spell, create a 1/1
white Dog creature token.
{r}{g}{w}, {t}: Rin and Seri, Inseparable deals
damage to any target equal to the number of
Dogs you control. You gain life equal to the
number of Cats you control.
"Alone in the world was a little"