Tarkus is a sergeant of the Blood Ravens Fourth Company.
A veteran of centuries of campaigning, Tarkus leads his Tactical Marines into combat with confidence and a steely demeanor. Slow to anger, Tarkus is a rock-solid second-in-command, and expert tactician.
Tarkus served with Davian Thule in the Kronus campaign, and quickly established himself as one of Thule's most trusted advisors. Tarkus twice distinguished himself in the campaign, first against the Tau, and once more against the Necrons, and was awarded Terminator Honors for his valor, after being selected to protect the bomb designed to bring down the Thur'Abis Plateau and bury the Necron force. During the fighting, Tarkus managed to neutralize a Tomb Spyder in the critical moments while the detonator was being armed. With no weapon that could damage the Necron horror, Tarkus rushed into the face of the Tomb Spyder and held a frag grenade in a joint near the head.
The explosion crippled the Tomb Spyder, but resulted in the loss of Tarkus' left hand and forearm (since replaced by cybernetics) and the heavy scarring on the left side of his face. However, this turned out to be a crucial point in the battle and gave the detonator time to go into failsafe mode, bringing down the plateau and burying the Necron base beneath it
In Dawn of War II, Tarkus is the only unit to start alongside the Force Commander in the first level of the campaign. Using frag grenades, Tarkus destroyed an entrance to Fellhammer Mine, blocking its use for the Ork invaders. Soon after, Tarkus deploys to find and rescue Sergeant Avitus, who had been incapacitated after a fight with the Orks in a key village. With help from Scout Sergeant Cyrus, Tarkus and the Force Commander eliminated the Orks, revived Avitus and recaptured the village from the Orks, before being extracted. Later, the Force Commander led the Blood Ravens strike team against two Ork leaders, one being a Stormboy leader, the other a minor Ork Warboss, killing both. However, as the battle went on, Tarkus, Avitus and the Force Commander deployed to Fellhammer Mine to re-capture it from the Orks. However, just as the strike team are advancing, an Ork ambush is sprung, but with an intervention from Thaddeus allows the strike team to advance again. After capturing a Communications Array, the strike team discover that an Eldar force is stirring up the Orks, and proceed to eliminate it and its leading Warlock in the process.
Depending on the player's decisions during the campaign, Tarkus can be used in other missions during the campaign, or can be left behind in favour of other squads.
During the battle for Angel Gate, Tarkus stays behind on Meridian to observe the clean-up operations, discovering House Vandis warehouses full of stolen Blood Ravens relics. With help from the Force Commander and his strike team, Tarkus captures and defends the warehouse, and later uses a salvaged set of Terminator Armour to assist the force Commander in defeating the eldar Farseer Idranel. Tarkus' last deployment is to the Typhon Graveyard, as part of the Strike Team that was to use bio-toxin weapons to damage the Hive Ships feeding on Typhon. After injecting 2 samples of the biotoxin, the Strike Team made its way to a teleport relay, and allowing the Blood Ravens 3rd Company to deploy to the Strike Team's aid. With help from Gabriel Angelos, the Strike Team eliminated the main Tyranid Hive Tyrant, and defeated the main Tyranid force in the sector.
In the year after the final battle on Typhon, Tarkus assisted in the purging of the Tyranids still in the sub-sector. When the distress signal on planet Aurelia was discovered, Tarkus deployed to the planet's surface with his squad of Tactical Marines, who were killed when the drop-pod was hit by surface defenses. Barely surviving, Tarkus still risked himself to draw the attention of entrenched enemy squads away from the approaching Force Commander. Depending on the player's choices, Tarkus may have participated in subsequent missions.
Again depending on the player's choices in mission objectives and wargear, Tarkus could be revealed as the traitor in the Blood Ravens. He had been corrupted by a daemon weapon, the Blighted Bolter that first appeared during the Aurelian Crusade and was exclusively used by Tarkus. The daemon promised him the power to save those he cared about and help the Imperium, thus using Tarkus' sense of morality to warp his mind. Shortly after the revelation, the Force Commander led a mission to execute Tarkus, who was armed with the most powerful and fully corrupt incarnation of the Blighted Bolter, still believing that he was saving his friends and comrades.
In Retribution, it is revealed that The Ancient is in fact Tarkus, who had taken a vow of silence after he had slain a fellow battle brother (who once served with him on Kronus) after the unnamed had answered Kyras's call.
In reference to the felled battle brother, Tarkus's words to you (Diomedes) were: 'There was another just like you.'
It is strongly implied that Tarkus had killed you, the Force Commander from Chaos Rising; an unnamed Space Marine Captain with very similar 'Traits', 'Abilities' and 'Wargear' predilection as Diomedes (who is also you, the Force Commander in Retribution). It isnt wild to assume Tarkus and you (in Chaos Rising) had a history together on Kronus prior to the first mission in Dawn of War (where you and Tarkus deployed together as the only usable units). It is mentioned in the Dawn of War first mission loading screen that not much about the (nameless) Force Commander's history is known since his most defining characteristic was his silence.
It is possible, but not likely, that Tarkus may have slain Avitus (just one of many Space Marines who served during the Kronus Campaign and we were introduced to) or some other unnamed Space Marine (who may or may not even be one of the known squad leaders from the previous titles but just a nameless squaddie) who might have served alongside Tarkus; no concrete fact is established on who Tarkus had killed, only speculation; though it was probably not intended to be a controversial issue given how straightforward the hints were. (it was you)