Cyrus is a Scout Sergeant in the Blood Ravens 10th Company, serving under The Force Commander in the 4th Company during Dawn of War II and Chaos Rising and under Captain Diomedes in Retribution.
Background[]
Cyrus was formerly a member of the Deathwatch, an organisation that excels at combating xenos, and because of this, he knew much about the Tyranids when they arrived to consume the Blood Ravens recruiting worlds. Cyrus prefers untraditional methods of warfare which often receive negative criticism from his fellow Space Marines, but because of it he joined the Deathwatch. He has a cybernetic eye, but does not reveal where or how he got it. Cyrus seems to be quite experienced for a Scout and it seems likely he stayed in the Scout Company due to his expertise and to train future Initiates, similar to Torias Telion of the Ultramarines.
Dawn of War 2[]
Cyrus was part of the Force Commander's task force sent to sub-sector Aurelia to defend it against the Ork invasion. Cyrus assists the Commander and Tarkus in searching for and reviving Sergeant Avitus. Cyrus also puts his Deathwatch experience to good use by regularly explaining both the nature of the Tyranids and what military tactics are effective against them.
Cyrus has access to specialist weapons such as Sniper Rifles, Flamers and Shotguns making him adept at taking out enemy infantry. He also has the ability to sabotage enemy structures or kill enemy squads with explosives. Cyrus and his squad can also infiltrate allowing them to sneak past enemies, gain intelligence, plant explosives or find an advantageous location for a firefight (for example taking up a spot behind enemies while the other squads advance).
Depending on the player's decisions during the campaign, Cyrus can be used in other missions during the campaign, or can be left behind in favour of other squads. Overall his is a very "light" squad that isn't very effective in combat in general, so using up one of your 4 key member slots for him compared to what else is available usually isn't appealing. One key issue of this, Cyrus is the only infantry squad member who will never be able to wear Terminator armor, and therefore won't be able to get access to heavier equipment or weapons. However, one skill he can gain with enough points in Stamina is a reinforcement beacon, a toggled skill that will let him reinforce lost squad members anywhere, although it has a moderately lengthy cooldown.
Cyrus' last deployment is to the Typhon Graveyard (all squads are deployed during this mission), 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 saving sub-sector Aurelia.
Chaos Rising[]
A year after helping purge sub-sector Aurelia of the Tyranid threat, Cyrus is still serving within the Force Commander's task force. After the Blood Ravens discovered a distress signal on the planet Aurelia, a world thought lost to the Warp, Cyrus' squad was deployed onto the planet alongside the Force Commander, only to discover that the signal was a fake and that the rebel House Vandis forces were waiting to ambush them. Cyrus and the Force Commander fought through the traitor Guardsmen to find the rest of the Force Commander's squad. Depending on the player's choices, Cyrus can partake in Missions throughout the Aurelia sub-sector. He will also occasionally offer advice before and during missions.
In terms of general combat ability, Cyrus has not improved much. He is still an extremely "light" squad that not only does very low DPS but also cannot wear any heavy armor, which means he is permanently fragile and will die often. Sacrificing one of the squad slots for him is still questionable except on missions where he must join otherwise he may become Corrupted.
Depending on how corrupt he becomes, it may transpire that Cyrus is the traitor within the Blood Ravens. The seeds of Cyrus' corruption were planted during the Kaurava Campaign as the loss of so many battle brothers seriously angered Cyrus and he blamed it on both the incompetence and corruption within the Chapter's leadership. He began to harbour a deep hatred and mistrust of those who led the Chapter, in particular Kyras, Diomedes, Davian Thule, Indrick Boreale and Gabriel Angelos. This hatred led him to be susceptible to Kyras and sparked his defection to the Black Legion.
Given that Cyrus shows up in Retribution, him becoming the corrupted traitor is strictly non-canon.
Retribution[]
10 years after the events of Chaos Rising, Cyrus is under the command of Captain Diomedes who aims to both restore the honour of Kyras & the Chapter and also to prevent the incoming Exterminatus. Though their relationship is somewhat hostile, due to Diomedes' ignorance towards Kyras' true nature.