[Poptartu]

Have each party able to deplete it's own health bar, but make it take several fights to actually kill it. 5 or 8 parties maybe, doesn't seem too big or too little. If not enough people are around to take it down it could be problematic unless there's a timer, with a partial reward based on how many groups beat it.

Could give it random drop chance, make the reward be some murai for defending against the threat, this feels like end game, so xp isn't the thing you'd want. A pile of 3-5 thousand murai would get you whatever piece of gear you're looking at though.