"Hellgate: Karakura Town" is a 5 man minimum event where joining sends you to an alternate Karakura town where your job is to locate a Hellgate(like the entrance to the Kushanada's area) that spawns in 1 of 5 locations and break it by reducing it's "health" to 0. When the event officially begins the Hellgate opens and spews forth Zombies until it gets down to 1/4th health left and begins spawning Kushanadas. Killing the enemies it spawns is completely unnecessary since destroying the Hellgate itself but it has no set spawn number so would eventually flood the surrounding area with both zombies and kushanada until destroyed.
During the event there is a secondary "Time Elapsed" objective that decides just how much EP you receive for destroying the gate. The longer it took to destroy the Gate, the more EXP and $ got from killing the creatures it spawns but the less EP you get for taking longer to complete. A stronger group would be able to finish the gate quicker, raking in the EXP, where a weaker group would have a harder time clearing out the enemies and navigating attacks around their numbers to destroy the gate itself.
During the event there is a secondary "Time Elapsed" objective that decides just how much EP you receive for destroying the gate. The longer it took to destroy the Gate, the more EXP and $ got from killing the creatures it spawns but the less EP you get for taking longer to complete. A stronger group would be able to finish the gate quicker, raking in the EXP, where a weaker group would have a harder time clearing out the enemies and navigating attacks around their numbers to destroy the gate itself.