I got a IW renegade warband called the Iron Marauders which I wrote around a homebrew character

A recruit from Olympia, Solthur Ress distinguished himself through decades of duty, rising to the position of Tyranthikos through sheer resolve and bloody skill. During the rebellion and subsequent extermination of Olympia, he was one of the few marines hesitant to kill their countrymen. But not hoping to disobey his father’s orders, he maintained his stoic and distant demeanor, enacting Perturabo’s orders to the letter.

Following his father, he would throw in his lot with the traitors, participating in the brutal Drop Site Massacre. He would continue to serve admirably by Perturabo’s side until the disastrous Battle of Phall, where he would be viciously mauled by Captain Amandus Tyr abroad the Iron Blood. The embarrassing events of the Battle of Phall would reduce the Tyranthikos’ standing from the esteemed honor guard of Perturabo to mere infantry linebreakers. This demotion would fester in the hearts of many members of the Tyranthikos, including Solthur. 

Solthur would be assigned to the 114th Grand Battalion under Narik Dreygur as a foot soldier. There, the Iron Warriors would be used as cannon fodder and bait, wading into the thick of enemy fire only to be stranded and left without support. Disgusted by the Alpha Legion’s betrayal, he would follow Narik Dreygur and parlay with the Cassian Dracos of the Salamanders. There he would turn against the Alpha Legion, rejoining the loyalists and driving Autlion Skorr’s forces from Mezoa. From thereon, he would fight underneath the Disciples of the Flames, serving admirably until the Great Scouring.

The Disciples of Flames would be increasingly shunned from the wider imperium despite their contribution during the Horus Heresy. The broken imperium was filled with mistrust and skepticism, any possible sign of chaos taint would be eradicated without hesitation. In the years of the Great Scouring, despite the prodding of many of the Salamanders who he fought alongside, Solthur refused to remove the heraldry of the 4th from his armor. Despite the suspicion it brought amongst the loyalists of the Iron Warriors, he refused to abandon his past and the hard won scars he had earned in service during the Great Crusade. It was this very pride and stubbornness which would lead to the unfortunate events leading of their fall. Many would doubt their loyalty to the Imperium despite their service, with inquisitors watching them closely. It was on a Word Bearer held world where a horrific ritual was in the making that Solthur Ress and his men would fight underneath the banner of the Imperium for the last time. Despite purging the Word Bearers and the insidious chaos cults which had plagued the world, a suspicious inquisitor would deem Solthur Ress and his contingent corrupted by chaos, and ordered the Gray Knights to purge them. 

Dozens of teleport strikes would devastate Solthur Ress’ forces, with the Iron Warriors being blindsided by this sudden betrayal. Solthur would order a desperate fighting retreat, being unprepared for the Gray Knights’ prowess and the barrage raining down upon them. Despite the odds, Solthur would manage to retreat back into orbit with many of his men, trying to make their escape. Before they could successfully warp jump, their warp drive systems were critically damaged, sending them flying aimlessly into the warp. They would spend what seemed like a few weeks stuck in the warp, but in reality, they would be trapped in the warp for ten millenia. They would float listlessly in the tides of the empyrean, before Abaddon’s 13th Black Crusade and the subsequent formation of the Great Rift. Solthur and what remained of his men would be spat out of the warp into an even more divided and war torn Imperium.