Maeleum

Maeleum was the Sons of Horus' post-Heresy daemon world, a rust-graveyard where they raised the Monument around Horus's corpse. Emperor's Children under Fabius Bile wrecked the fortress and stole the body; Abaddon abandoned the ruin when he remade the Black Legion. Thagus Daravek later cored the planet for mass-driver shot.