Hira and Elric, 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}: Hira and Elric, 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.