Giants and Titans are level 7 creatures of Tower town. They are recruited from the Cloud Temple.
"Giants and titans are immune to spells affecting the mind. Titans do 150% damage to black dragons, can hurl lightning bolts in a ranged attack and suffer no penalty for hand-to-hand attacks, making them the most powerful ranged attack unit in the game." RoE manual
Titans are one of the two upgraded tier 7 units that occupy one hex, the other being Arch Devil.
The ability to "burn with anger" and do extra damage to black dragons is likely a reference to 3DO's previous title Heroes of Might and Magic II. In that game, the Wizard and Warlock were widely considered to be the strongest heroes and there was some debate among players as to the single strongest 6th level creature.
See also: