Earthen Root Enclave Dungeon Guide ESO

The first secret boss is found in the grassy area at the beginning of the dungeon. It is a fire-wielding Spriggan called Scalded Roots, however it will be inactive to begin with. If you defeat this boss, you will get the Scalded Strength buff for the rest of the dungeon, giving you and extra 500 weapon and spell damage.

How to Activate Scalded Roots

To activate the boss, you will need to find three bonfires scattered around the area and light them. The bonfires are guarded by trash enemies, so be careful when doing this. After all three are lit, a red orb will spawn and start moving to the boss. This orb is just a guide to help you locate the boss though, and you do not need to wait for it to arrive before starting the boss. Once all fires are lit, you simply need to approach the boss and it will activate a few seconds later.

How to Defeat Scalded Roots

Scalded Roots has around 3 million HP. 

Fireball

The boss will throw a fireball at whichever player has aggro. This fireball does some direct damage, and will then spawn a small fire AOE underneath the player that was hit. This means that the tank will need to gradually move around to avoid taking too much damage from these fire AOEs, and the rest of the group should be wary of this and avoid standing next to the tank.

Meteors

She will also periodically throw fire meteors at random players in the group. These do quite a lot of damage but not enough to one-shot you, so shouldn't cause a problem as long as you have some healing. 

Cleave

The boss has a small conal cleave attack, so the group should avoid standing in front of her and just let the tank deal with this. 

Fire Wolves

Finally, there will be fire wolf adds that spawn throughout the fight. These do not do much damage and can be taunted. Really they are just a minor nuisance and should not be a problem, just make sure you have some AOE damage in your group and they will die.