An aquatic vector of the Mind Worms, the Isle of the Deep is closely associated with Mind Worms and Sea Fungus. The floating shell of an Isle of the Deep, formed by the secretions of the colony's individual members, is often used as a nesting place by Mind Worms, and can even float large land units.
Isles of the Deep and other alien creatures can engage in Psi Combat in which weapon and armor strengths are ignored. Morale level is quite important in defending against Isles of the Deep and other alien units.
With proper breeding and bonding techniques, Isles of the Deep can also be bred in captivity and controlled by skilled brood trainers. These captive boils can be used to attack enemy naval units using Psi Combat. Depending on their size, they can also be used to transport land units. Like any native unit, players can also release Isles into the wild, to harass and disrupt an enemy.