Kraken's Eye

Whenever a player casts a blue spell, you may gain 1 life.

It's seen the wonders of entire worlds trapped in the depths of a bottomless ocean.

Magic 2012

Salvat 2011

Magic 2011

Duels of the Planeswalkers

Magic 2010

If a player casts a blue spell, Kraken’s Eye’s ability triggers and is put on the stack on top of that spell. Kraken’s Eye’s ability will resolve (causing you to gain 1 life) before the spell does.

The ability triggers whenever any player, not just you, casts a blue spell.