Trajann Valoris
He was silent as I spoke, but slowly reached up to his helm and took it off. I don’t know what I was expecting to see – perhaps something like Valerian had been, with his smooth skin and pleasant complexion. Valoris was nothing of the kind. His visage was hard-edged, broken by scar tissue, the skin veined and vivid. His lips were thin, his nose flared, his neck sinewy. In that low light, no doubt amplified by my own fear, he looked almost ghoulish.
-- Lev Tieron, Imperial Chancellor, on Trajann Valoris
Trajann Valoris is the current Captain-General of the Adeptus Custodes, and as of writing he is the only named HQ available to the Custodes that can be fielded on the tabletop. He features prominently in the novel Watchers of the Throne, where he is convinced by the-then Imperial Chancellor Lev Tieron to take a seat on the High Lords of Terra in the hopes of overturning the law keeping the Custodes tied down to Terra (officially; unofficially the Custodes have been ranging far and wide since at LEAST the 36th Millenium according to their Codex). Said law eventually got repealed anyway, partially due to the action of a technically-unsanctioned mission of Custodes and Sisters of Silence, but it can be assumed that him being part of the bureaucracy now helped formalize the return of the Talons of the Emperor to the battlefields of the 42nd Millenium.
On a side note, his portrayal in the Codex does not match up AT ALL with how he was described in Watchers of the Throne.
Codex Biography
Valoris took over the post of Captain-General when his predecessor Andros Launceddre fell at the Battle of the Black Pyre. Many claim that he's the greatest warrior ever to hold the position since the Horus Heresy. In his first decade of service alone, he ran two successful Blood Games, and this record remains unbroken in the present day. During his tenure among the Allarus Custodians participated in the destruction of the Space Hulk Mournful Siren and the defeat of the Genestealer Cult of the Emperor's Writhing Shadow, earning many names for his deeds.
Valoris has been noted to be unusually proactive, preferring a strategy of so-called "active defense"; in his years of service he has often led pre-emptive strikes, and at the same time cultivated networks of informants and agents across Segmentum Solar and beyond to keep him abreast of emergent threats. He is aware of his own aggressiveness however, and tries to temper it by doing as much research and preparation as possible before committing to an attack, so that none of his comrades lives would be needlessly lost as a result.