Main mission - Enemy at the Gates | Act 4 Dungeon Siege III Guide

Head to the southern tunnels (M30,4) and look for the powder satchels (M30,5). During the exploration of the labyrinth you will have to use platform-calling crystals - their locations have been marked on the map for your convenience (M30,6).

If only you keep the enemy at distance, you should be fine.

After you collect the charges, head for the boss (M30,9). Once he's down, throw the powder satchels into the mine cart and run.

Once you finish this mission and Uninvited Guests, you should head to the Queen to activate Ebb and Flow.

M30 - Southern Mining Tunnels