Seeing some of the discussion going on regarding this item, I've a modest suggestion: Single use item, variable number of apes summoned on use (perhaps 2d4). Something more to consider-- change it so using the barrel breaks invisibility.
I like the concept; it's a malicious item that has potential to enhance RP rather than simply troll other players with, IMO. At 50 charges with one ape (relatively weak creature, IIRC) summoned per use, there's little risk involved in using the item, even when the faction is fixed; the player can simply aim the summon origin far away, or close to something else. Being able to use the item continuously while invisible further makes it so that even innocent intention can quickly become irritating. I'd imagine if the item was made single use with the number of apes summoned an uncertainty, these apes wouldn't be summoned as carelessly as they are now. And if using this item would break invisibility, it remains more of a risk to use.