The Morlocks were elite members of the Iron Hands Adeptus Astartes that wore Terminator armour.
They were named after predators from their homeworld of Medusa III and were the toughest warriors within the Legion. As such, they often stood guard at the Anvilarium on the Fist of Iron where Ferrus Manus resided.
A detail of Morlock Terminators that watched over their Primarch were killed when Fulgrim's Phoenix Guard turned traitor and slaughtered them during the early stages of the Horus Heresy. The remaining Morlock's were transfered onto the Ferrum for deployment with the Loyalist Legions against the traitor forces at Istvaan V. 1
Source
- 1:Fulgrim by Graham McNeill