Nether Surges are one of four random events that can happen in the world of Nether.

Nether Surges Can take place in these locations:

A Nether Surge is a horde of enemies in one location and the aim is to kill all Nether and exterminate the horde before the time limit is up. The Nether Surge features a percentage meter indicating how many Nether have been killed out of the total horde. Surges last for 20 minutes.

These events are great for EXP but is notably dangerous if you are not properly equipped.