Description of effectFire-type moves become stronger when Pokémon is low on HP.
Physiological Response - BiologicalWhen the Pokémon experiences great pain and weakness, the body produces a unique adrenaline that triggers a chemical reaction in the Pyro-Sac (responsible for Fire-type Pokémon's ability to breathe fire), creating substance(s) that ignite more powerfully than normal, but cannot be produced willingly since the Pyro-Sac wasn't built to withstand the excess strain, and the higher temperatures have risk of self-injury over long-term use.
Physiological Response - PhysicalNone known besides those related to activing Ability, see below.
Psychological Response - MentalThis ability has no known effect on a Pokémon's mental processes or abilities.
In battle ResponseWhen the Blaze Ability of Pokémon activates, the flames on its body burn much more intensely. Additionally, when an offensive Fire-type move is used, its power greatly increases.
Environmental ResponseThis ability has no known effect outside of battle.
Further ResearchResearchers are currently studying how exactly the Ability affects Pyro-Sac and the fire Pokémon is using, largely in hope of even more effective heat-resistant items as well as higher-quality anti-burn medicine. Another research focuses on why Pokémon most likely to be seen with this Ability are group which Trainers nickname as "Fire-type starter Pokémon".
Pokémon with this abilityCurrently, this Ability has been observed at 17 different Pokémon, with two of them having as a rare sub-group known as 'Hidden Ability', remaining 15 having it as their common Ability. The Pokémon with this Ability as common Ability are Charmander line, Cyndaquil line, Torchic line, Chimchar line and Tepig line, all of which are known to be sometimes handed out by Prof. Oak, Prof. Elm, Prof. Birch, Prof. Rowan and Prof. Juniper, respectively. The other two Pokémon which have this Ability as Hidden one are Pansear and Simisear.
[-Written by Pink Celebi with help of J.N.L.J]