The ability triggers whenever any player, not just you, casts a red spell.
01-10-2009
wotc
If a player casts a red spell, Dragon’s Claw’s ability triggers and is put on the stack on top of that spell. Dragon’s Claw’s ability will resolve (causing you to gain 1 life) before the spell does.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.