Olog-hai

In J. R. R. Tolkien's fictional realm of Middle-earth, The Olog-hai were a fierce breed of Trolls which appeared during the last days of the War of the Ring in Sauron's service. They shared none of the old Troll vulnerabilities: they were very intelligent, able to move under the sun, and very menacing. For this reason they were seen by some to be Orcs like the Uruk-hai, but they were definitely of Troll stock.

They only spoke Sauron's Black Speech, and it is possible they only existed because Sauron's will empowered them.

The Olog-hai do not actually appear in The Lord of the Rings: they are only mentioned in the Appendices. It is however possible that some Ologs were present at the Battle of the Pelennor Fields.