Tom, Bert, and William

Tom, Bert, and William, also known as The Trolls, were creatures that Bilbo and the dwarves encountered on their journey to reclaim Erebor.

The trolls originally came fromthe Mountains, forged by evil forces.

Bert
Bert was portrayed by Mark Hadlow, who also portrayed Dori.

William
William was voiced by Peter Hambleton, who also portrayed Gloin.

Tom
Tom was voiced by William Kirsh, who also portrayed Bifur.

Quest of Erebor
The Trolls held Bilbo hostage and

threatened to ripped him apart, but Thorin, not risking losing a member of his company, stood down.

Legacy
Sixty years later, Bilbo wrote his adventures in a book known as the Red Book of the Westmarch, including Bert, Tom and William.

Frodo's Injury: Return of the Trolls
Bilbo mentions the trolls on how they should cook Bilbo and his allies. The trolls' previous victim, Bilbo Baggins' nephew was stabbed by the Witch-King of Angmar. Aragorn later finds their statues are once again and uses it as a guide to get to Rivendell via the hidden passage way. When Frodo lies there, Sam points out that its the Trolls from Bilbo's stories.