Sludge

Sludge (スラッジ) is a boss in Golden Sun: Dark Dawn. It is a lizard-like monster that haunts the Phantasmal Bog and, by extension, Kolima Village.

In Golden Sun: Dark Dawn
Sludge is the boss of Phantasmal Bog and is fought at level 24. When Sludge is defeated, the party immediately gains the Crush Tusk, which bestows the Crush Psynergy to a Mars Adept when equipped. Sludge's statistics are as follows:

Sludge uses these battle commands:

Strategies
The battle with Sludge is similar to the Star Magician, in that Sludge can call upon allies, his Skulls, to assist him in battle. Sludge has access to an apparently unlimited number of skulls, though only three can appear in battle at any one time. Unlike the Star Magician, however, the battle with Sludge is fairly easy, relatively speaking. Most of Sludge's own attacks are fairly weak, though the player must be alert of the Skulls that accompany him.

All of Sludge's skulls are capable of physical Attacks. Additionally, The Shield Skull can reduce the amount of damage Sludge takes, the Curse Skull can inflict the Curse status, or potentially down unlucky Adepts with Condemn, while Haunt Skulls can inflict the Haunt status via Witchlight. While the curse status can easily be removed via Restore, the player should have Dewdrop handy to heal any Haunted Adepts. An Adept with Revive is also handy for Reviving any victims of Condemn.

Sludge and its Skull minions are all weak to Jupiter-based attacks. Thus, unleashing Jupiter Djinn and summoning Thor is an excellent offensive strategy. Alternatively, the player can use Jupiter-based Psynergies to do damage. While concentrating on Sludge will help end the battle quickly, the existence of the Skulls mean the battle is excellent for gaining experience. Should the player wish to take advantage of this, they should instead focus damage on the Skulls. Having a designated healer can assist in this strategy, by healing the damage from Sludge's attacks so that the battle can be prolonged.

Story relevance
Sludge was once an inhabitant of marshland located near Saha Town. After the Golden Sun event moved Kolima Village and Kolima Forest on top of the marshland, Sludge's home was destroyed. Sludge took to haunting the area underneath the Village, and placed a curse on the area surrounding Kolima Village. This not only caused Kolima Forest to become un-navigable, but sickened Kolima's Dream Tree, causing Kolima's Dream Leaves to cause nightmares.

Matthew and his party encounter Sludge while they are exploring the Bog after eating the cursed Dream Leaves. Sludge is seen using Crush to destroy parts of the pathway that Matthew is taking. After reaching the end of the Phantasmal Bog, Sludge attacks the group. Defeating Sludge reverses its curse, allowing the party to continue on their quest.