Whenever you cast a white spell, Thistledown Duo gets +1/+1 until end of turn.

Whenever you cast a blue spell, Thistledown Duo gains flying until end of turn.

Whenever you cast a blue spell, Gravelgill Duo gets +1/+1 until end of turn.

Whenever you cast a black spell, Gravelgill Duo gains fear until end of turn. (It can’t be blocked except by artifact creatures and/or black creatures.)

Whenever you cast a black spell, Emberstrike Duo gets +1/+1 until end of turn.

Whenever you cast a red spell, Emberstrike Duo gains first strike until end of turn.

Whenever you cast a red spell, Tattermunge Duo gets +1/+1 until end of turn.

Whenever you cast a green spell, Tattermunge Duo gains forestwalk until end of turn. (It can’t be blocked as long as defending player controls a Forest.)

Whenever you cast a green spell, Safehold Duo gets +1/+1 until end of turn.

Whenever you cast a white spell, Safehold Duo gains vigilance until end of turn.