Rex Mundi is a fictional immortal character from Malibu Comics' Ultraverse imprint. He has played important behind-the-scenes roles in most of the Ultraverse's major events, beginning with the downfall of the Fire People. Rex Mundi was revealed in Phoenix Resurrection: Revelations to contain part of the Entity, a vastly powerful alien device that was scattered across Earth, the Moon, and the Sun four billion years ago, and were ultimately responsible for the existence of not only Mundi, but most of the other Ultras in that universe. His fate after that time is unrevealed, mainly due to the subsequent folding of the Ultraverse line, but it was revealed that he has a daughter, Glorianna Mundi.