Acid Rain

Acid Rain is a Poison-type move introduced in Generation Omega. It can only be learned by Nucleon by level, but can be taught to Poison and ??? Pokemon with VM08.

Type: Poison

Category: Status

When used, multiple weather conditions appear at once: sun, rain, hail, and sandstorm. Pokemon take damage four times due to these conditions, even sun and rain which normally don't (hence the name Acid Rain). The damage becomes equal to 1/4 of the Pokemon's max HP (1/16 * 4). However, several conditions are different under acid rain.

Type immunities to these conditions are ignored (that is, an Ice-type will take damage due to hail). Ice Body will instead heal the Pokemon during hail as Ability immunities/changed effects due to them are not ignored (but it is still hurt under the other three conditions, effectively reducing the damage dealt to 1/8 of max HP). Interactions between multiple weather conditions remain and always stack. Items that block all weather damage stop all four Acid Rain effects. Also, Poison and ??? Pokémon are unaffected by all of Acid Rain's damage. (Here is a list of interactions I believe to be definitive. ~Rotamaster Chaos)

The damage boosts from sun and rain cancel each other out because they are simultaneous. Dry Skin effectively does nothing because of the weather (as rain heals, then hurts and sun hurts twice). Solar Beam and Solar Blade do not need a charge turn but have their damage reduced by 1/8. Cherrim stays in its Sunshine Form due to the presence of sunlight. Furthermore, Weather Ball becomes Poison-type and its power becomes 400!. Moonlight, Synthesis, Shore Up, and Morning Sun all recover 2/3 of the user's max HP. Blizzard, Thunder, and Hurricane all bypass accuracy checks due to their weather effect causing this being present.

The name is a reference to the acid rain glitch from Generation 4, that causes these multiple weather effects to be present concurrently. Its properties are similar to the ones Acid Rain would have if in Generation Omega.