The Leviathan is very tanky, has a powerful (but slow) attack, and a multi-targeting special ability. A great all around tower.
Tier 3 (upgraded) Tower/Fighter
Upgraded from a Tempest
245 minerals / 2 population
Armor Type: Massive
Damage Type: Siege
Shrapnel: Missiles fired from the Leviathan explode, dealing 120 additional piercing damage to 3 nearby units