The Coastal Mine Puzzles and Chests

Upon entering The Coastal Mine, defeat the two Goblin Loyalists. Use the mine cart to proceed.

Follow the path, light the unlit furnace with Incendio or Confringo. This is crucial for later access to a switch.

Pull the nearby platform with Accio to cross a gap.

In the large room with multiple paths, defeat the Ranrok Loyalists. Use spells like Expelliarmus and Ancient Magic.

Head north to find another furnace. Light it to call a lift. Take the lift down to face Grodbik, a Level 30 Infamous Foe, and other Goblin Loyalists. Focus on lesser goblins first to build Ancient Magic, then defeat Grodbik. Deal with the Fortified Troll afterwards.

Locate a Legendary Chest at the back of the room near where the Troll was.

Light the furnace to the right of the lift (when facing it) and take it back to the top.

Ignore the platform to the south (leads to objective). Continue up the stairs and to the right.

Use Accio on the manhole cover and drop down. Follow the path to find the first Collection Chest. Exit through the door and take the mine cart back.

Take the other path by using Accio on the platform and ride it down.

Defeat the Goblin Loyalists in the new area.

Take the mine cart in front of you. This leads to a switch that powers the first unlit furnace. Pull the switch with Accio to open a door and access the second Collection Chest.

Return via the mine cart. Take the path to the right of it to another unlit furnace. Activate it and take the lift down.

Follow the path into the cavern and prepare for a battle against Goblins and a Troll. Focus on the Goblins first, using barrels for explosive damage.

Once enemies are cleared, use Revelio to highlight the pillars near the drill. Use Confringo to destroy them and disable the drill.

Story scenes will conclude, returning you to the mine entrance. Leave the mine to end the Main Quest.