Foul-Tongue Invocation 
Instant
As an additional cost to cast this spell, you may reveal a Dragon card from your hand. Target player sacrifices a creature of their choice. If you revealed a Dragon card or controlled a Dragon as you cast this spell, you gain 4 life.
Legality
standardNOT LEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL