The swarm is an Abysal Boss rush.
Defeat your enemy, upgrade your stats, go to the next boss and repeat !
use your remaining life points (materialized by little glowing fireflies) to deal damage.
You can only be killed if there is no more firefly surrouding you.

How many creatures will you deafeat before being vaniquished ?

The Game is still in BETA.
Upcoming Updates will add new contents but all the main Gameplay mechanics are already there.