Not much is known about Titan's origins or his relation to the Atlanteans or Sub-Mariner. All that is known is that Titan wishes to rule over the land and lay waste to any surface dwellers.
Titan was created by Dan Slott and Rafa Sandoval and first appeared in The Mighty Avengers #24.
Titan has not featured much since his first appearance, his only other appearance was a cameo in The Mighty Avengers #35.
Major Story Arcs
Titan randomly attacked Biarritz in France in pursuit of conquest of Earth. He was met by the Avengers (Amadeus Cho, Hercules, Quicksilver, Stature, U.S.Agent, Vision and Wasp) and G.R.A.M.P.A. agents Blackjack (Ace and One-Eyed Jacquie). It fell to Stature and Wasp to engage Titan and prevent him from reaching further in-land due to his immense size dwarfing over the rest of the Avengers and Blackjack.
Forced to grow to their absolute upper limit, Stature and Wasp battled Titan to the point where the beast had started to become weak due to having being away from water for too long. As the giants duked it out, Hercules and Vision attempted to blind the beast by having Vision fire a solar beam onto an enlarged mirror and directing the light into Titan's eyes. Alas, the attempt only enraged Titan who continued to fight Stature and Wasp.
Elsewhere, Amadeus, Blackjack and U.S.Agent armed themselves with an assortment of guns which would fire a special saline mix Amadeus had developed which would draw all the moisture out of Titan, thus further weakening him.
Titan attempted to flee to the sea to absorb some water and replenish his strength, battering off the attacking Avengers on his way. Using his super-speed to circle Titan, Quicksilver was able to make the monster lose his balance and fall off - thus defeating him. Titan was then taken into custody by G.R.A.M.P.A. and held within a special facility.
Powers and Abilities
Titan is a gigantic sea creature. Most of his power and strength stem from his size but as seen if he is away from water too long his strength begins to waver. Titan has multiple tentacles which he can use to further cause damage.