Trolls can appear alone, with Bulls and with ZomBulls. They're mainly found in the middle of the game.
Troll hate light, troll hate fire, fire bad!! Also, being a creature of the Regenerative category, these things regain HP every round and are weak to the Flame Sword in the WSC version.
Troll is still Troll in every version. Trolls come from Teutonic myth and live in mountains and caves. Trolls are everywhere! You can find them in Dungeons & Dragons, The Hobbit and Lord of the Rings, the Warcraft series, and as little toys with wild hair and (usually) jewels on their bellies. In fact, as I type this, my neice is downstairs watching a movie called A Troll in Central Park, starring Dom Deluise. Trolls return in FF9.