Modes - Onslaught
In Onslaught mode, the player chooses a character to go against an unending number of monsters, where the goal is to take down as many monsters as possible before the player character's HP reaches 0. Every time 20 monsters are defeated, a medical kit to fully restore your character's HP will appear in the middle of the Onslaught arena.
Onslaught mode begins rather tame, with only Ghosts for the first 10 enemies, but pretty soon, the arena will be filled with loads of projectiles and enemies rushing from every direction as the number of slain enemies increases. Characters with Defense, Projectile, Summoner and/or Heal tags generally perform well in Onslaught, as they can make more mistakes and suffer less for them, but Offense tagged characters should not be discounted, either, as many of them can rage through enemies very quickly (though less room for error), Speed tagged characters can dodge roll through a greater amount of projectile swarms and Area Control characters can hit large numbers of enemies at once.
Whatever your strategy for Onslaught mode, medical kit management is very important, as stretching out your character's health as much as possible before grabbing the medical kit can make all the difference prior to the next one appearing every 20 monsters. In particular, keep an eye out for Windmills and Indestructibles, whose knockback attacks may launch you into the medical kit before you actually plan to pick it up.