Use your health potions, wear strength gear for higher health pool and get gear with h/s on it to regenerate your health faster that is all the ways to do that. Health potions are the red jars on the bottom right of your screen. You can buy more from Ellie in Forest Haven.
Weapons give procs like when you use a staff it will have a random chance to debuff a mob.
That is the number of mobs left to kill in a dungeon when it reaches zero all the mins are dead and you move on to the next dungeon.
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