Plasma Canister Harpoons are a type of ammunition in Horizon Forbidden West compatible with only one Ropecaster. While it deals very low Impact damage when attaching to a target, the canister can be set off by Plasma arrows, triggering an explosion that deals high Plasma damage and very high Plasma buildup.
It can be used to prime a Plasma Blast on an enemy, where after a certain amount of time, they will explode. This explosion will inflict more damage if the target has taken additional damage during the countdown of the status effect. Effective against enemies with plasma vulnerability.