When even deeper wellsprings of grief and anger in the world's people gather, they give rise to these mean monsters. They're both stronger and tougher to take out than their Nightmare cousins. — Description, Sonic Unleashed
The Deep Nightmares look much like the regular Nightmare, resembling humanoid chameleons with thick forearms and have purple smoke emitting from their back, but they have some distinguished traits as well. They are slightly taller, their horns and tails are larger and more jagged, they have several more teeth with tusks in the corner of their mouth, and they have larger and more spikes on their back. Also, their skin is colored a darker blue and their marking glow in a darker electric crimson.
Powers and abilities
The Deep Nightmares are able to move around by teleporting into an area in a puff of purple smoke, or emerging from black puddles on the ground. As a Dark Gaia Minion, the Deep Nightmares can possess people by latching onto the deepest, darkest part of the heart, and generate despair, negative emotions or even erratic behavior that are completely opposite to the person's personality.
Being an evolved form of the Nightmare, the Deep Nightmare has strength, speed, durability and intelligence above the regular Nightmare. They possess elastic bodies, allowing them to stretch their limbs over a slightly larger area. They can even enlarge their limbs and amplify the power of their physical strikes with dark energies, though doing so exhaust them and leave them weak and invulnerable afterwards for a few moments.
The Deep Nightmares have a certain degree of skills and cunning in terms of hand-to-hand, being able to fighting opponents with combos and guard against attacks with their arms. They can also use the spines on their backs as melee weapons.
The Deep Nightmares were born in the beginning of Sonic Unleashed. When Dark Gaia fell apart from its premature awakening, many of its fragments became Deep Nightmares by the influence of the negative energy from people's dark feelings, specifically from the deeper wellsprings of people's grief and anger. They first appears in Windmill Isle Night Act III: Hill Beneath Starry Skies on the Wii/PlayStation 2 version and Windmill Isle Night Act 1 on the PlayStation 3/Xbox 360 version.
The Deep Nightmares have much faster movements, can deal more damage, have more health and are more tactical than the regular Nightmare. Unlike the normal Nightmare, the Deep Nightmares can appear alone or are spearheading lesser members of their kind. They also come in a stronger variant called Red Deep Nightmares.
In battle, the Deep Nightmare fights with hand-to-hand combat, but in a more aggressive way than the Nightmare. They usually strike with their stretchy arms and can make body flips that cause damage to Sonic if hit. They are also capable of aerial attacks; if Sonic jumps into the air, the Deep Nightmares can jump up and knock him down again. On the PlayStation 3/Xbox 360 version, they have a move similar to the Were-Tornado and Were-Cyclone, though they will shrink down from exhaustion and be vulnerable afterwards. When fighting defensively, they can nullify the damage from the player's attacks by guarding, which can be broken with the right combo attack or be automatically put down after a while, or jump backwards to dodge strikes. As the player advances, the Deep Nightmares will become faster, stronger and more refined defensively.
Upon the reconstruction of Dark Gaia by Dr. Eggman, all of the Deep Nightmares along with the other of Dark Gaia's Minions were returned to the beast, who was later defeated and sealed within the planet's core.