The subject of this article originates from non-canonical sources. To find out about what is considered "canon" see LOTR:Canon.
The Mordor Attack Troll is a breed of Olog-hai and unlike the Morgul breed, these are mostly covered in strong armour. There are only a few of these who managed to make it to the black gate in time for the battle as they are scattered all over Mordor and only one left at the end of the battle, who duels Aragorn. He, like the rest, fall when Sauron is defeated.
These trolls were hardy, strong, tall and covered in armour.