The concept of cultural items is very cool, I agree its a niche that main 5e really doesn't touch on, so its fertile design ground for some neat items.
That parasite launcher is just nasty! Where it comes in really handy is situations where the enemy doesn't have a reaction, such as surprise, or they used a maneuver or took an OA, or what's really likely....your party hits with 2 attacks (either from extra attack or from two characters each with this weapon) on the same target. In that case a hit is a minimum of 3d4 + dex damage....and probably 5d4 + dex against many creatures (though the parasite could do a total of 7d4 + dex damage with just a +2 prof mod, combat is too quick to rely on that, so I never assume more than 1 round of extra pain).
The action cost + 2d6 damage is probably too much of a penalty in most cases (especially if there are multiple parasites since you can only remove 1 per action anyway) . Sake of argument, I save 2 rounds of damage, that's 7 vs 10 average damage....aka saving 3 damage from the cost of an action, probably not worth it. I think PCs might use the action to avoid strife, monsters will probably just keep on trucking.
Just confirming: The way its written right now, the parasite does its 2d4 ongoing damage 3 times with a +2 prof (it does the initial 1d4, 2d4 on the creature's start of turn, and then it says it continues for prof mod rounds for another 4d4 damage). Just confirming that is intended, or is it meant to be 2 TOTAL instances of ongoing damage (in which case it needs a wording rewrite).
One "weirdness", if I launch a number of these at once, in some ways I would rather the parasite dying (to genertae the strife) was faster not slower. While damage is nice, strife is much stronger at higher level combats if you can get 2 or even 3 levels of it on a monster. With a +2 prof mod, I MIGHT just get some strife on a big bad, but at +3 or higher its going to take too long and its highly likely the combat will be over before it kicks in. So could I "lower" my prof mod to +2 for the duration of the parasite if I wanted to?
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