Though this is not confirmed, the pics would have you believe it’s Lorgar.
From Faeit 212. Here is the Wiki on Lorgar, the Word Bearers Primarch.
Lorgar, also once called Lorgar Aurelian and the Urizen before the Horus Heresy, is a Daemon Prince of Chaos Undivided and the former Primarch of the Word Bearers Traitor Legion. Always determined to uplift humanity through a deep belief in the divine, once the Emperor of Mankind rejected his attempts at worship, Lorgar discovered new Gods, the Ruinous Powers of Chaos, more worthy of his devotion during his infamous Pilgrimage. He was the first Primarch of the Space Marine Legions to fall to the corruption of Chaos before the Horus Heresy and it was he who ordered the corruption of the Warmaster Horus. He and his large Traitor Legion of Word Bearers Chaos Space Marines can today be found on the Daemon World of Sicarus within the Eye of Terror.
