Fire Pledge inflicts damage. It has a regular power of 50.
When two allies attempt to use Fire Pledge and either Water Pledge or Grass Pledge on the same turn, the ally moving first will not itself use a move, but instead the ally moving second will use a combined attack with a power of 150 and an additional effect immediately after it:
If Fire Pledge and Water Pledge are used in the same turn, the ally moving second will use Water Pledge with a power of 150, and create a rainbow on the user's side of the field for four turns. The rainbow doubles the probability of secondary effects taking place on that side of the field; this effect does not stack with Serene Grace.
If Fire Pledge and Grass Pledge are used in the same turn, the ally moving second will use Fire Pledge with a power of 150, and create a sea of fire on the target's side of the field for four turns. The sea of fire damages all non-Fire-type Pokémon on that side of the field for 1/8 of their maximum HP at the end of each turn.
If a Pokémon uses one Pledge move and a partner has selected another Pledge move, but none of its partners are able to use their selected Pledge move that turn (e.g. paralysis, Sky Drop, etc.), no move will be executed.
Fire Pledge is unaffected by a held Fire Gem (and will not consume it).
Generation VI onward
Fire Pledge's regular power changed from 50 to 80. In addition, Fire Pledge does not work in Sky Battles.
It damages an enemy. If it's used with Water Pledge in an Alliance, you and your teammates will get the rainbow condition, and if it's used with Grass Pledge, the enemies in the same room will get the sea of fire condition.
Pignite slams its hand on the ground, causing pillars of fire to rush towards its opponent. When the pillars reach the opponent, they form a ring of pillars and then merge into one giant fire pillar, damaging the opponent.