The Dread Dragon (Terror Dragon in the original version) is the prime darkness dragon appearing in the anime Mon Colle Knights.
It lives in the Realm of Evil and appears in the last three episodes, later becoming the Doomsday Dragon (Tyrant Terror Dragon in the original version) during its second appearance.
The Dread Dragon is first seen when it is summoned by Redda to attack Mondo and his monster friends. It holds Rockna, whom Redda had kidnapped earlier after the heroes and Extreme Fire Dragon had defeated the Daemond earlier, captive and traps her within its neck on his command, and absorbs Mondo's allies into a black hole. This dragon sports a number of unusual abilities, such as a paralyzing smoke, the ability to grow tentacles and stretch its neck to great lengths.
Rockna at one point gains enough control over the dragon's mind to stop it from killing Mondo. Afterwards, the freed Rockna and Mondo merge with Gabriolis and destroy it for the time being. Considering this defeat differed from earlier defeats by depicting the monster bursting apart, rather than fading, it can be assumed that it died. The next episode depicts it whole again, and Redda uses its body as a host for the revived Oroboros.
The ensuing transformation of the Dread Dragon into the Doomsday Dragon as Redda summons Oroboros and uses its body as its host sees the dragon itself bloodily torn to shreds through a chest burster as Oroboros grows out. Only the giant eye on the Dread Dragon's chest is incorporated into the dragon's newly-transformed body, which grows an extra head as well as an extra pair of wings. In this form, it gains the ability to mess with time and space: its left eye reverts time, its right eye speeds it up. It still has the ability to grow tentacles, but now it must mutilate itself for this.
Even after Redda's death by Gabriolis' hands, the Doomsday Dragon still continues its destructive course until Mondo, Rockna, and the Golden Dragon destroy it. This frees Oroboros and it returns to its respective realm.