The move is an auto-charge special; using the move once will make Piranha Plant charge up poison until it is hit, it charge-cancels the move, or reaches full charge (indicated by purple clouds coming out of the bottom of its pot or pipe). The attack itself involves Piranha Plant blowing a purple cloud of poison directly in front of itself that slowly moves forward before dissipating. The longer the move is charged, the larger and more damaging the poison cloud will be. Despite the move being a poison-based attack, it does not inflict the poison status effect; instead dealing darkness element damage. Opponents within the cloud are dealt multiple looping hits that have no hitstun but inflict damage very rapidly, with the uncharged move dealing up to 30% damage over its entire duration and the fully charged move dealing upwards of 50%. This allows for both powerful shield pressure into shield breaks and massive damage on dazed opponents. Since opponents will likely simply move out of the cloud or try to avoid it altogether, the move is ideally used either as an area denial tool or as the immediate prelude to a grab to hold the opponent inside the cloud. The cloud is opaque and obscures everything within it, which can also allow for mindgames, such as Piranha Plant hiding within the cloud to charge a smash attack or Long-Stem Strike. Piranha Plant turns yellow with red polka-dots, purple teeth and green lips when charging and when blowing the cloud.
This move is based on the Putrid Piranha, an enemy in the Paper Mario series. Most notably, the Putrid Piranha's design matches with the color scheme of Piranha Plant when using this move. When encountered, Putrid Piranhas spit poison which deals damage to Mario or his allies and subsequently poisons them.