Horus' body was taken into the eye of terror by the black legion, were fabius bile tried to clone him. however, the Emperors Children got into a fight with the black legion and stole Horus and destroyed his body. his mace was likely destroyed by the Emperor. abbadon did not destroy horus's body.
As pointed out to me by
YOU Erus, when you look at Saguinius's armour in the (in?)famous drawing of the confrontation between Horus and the Emperor, look at the wound in his side.
look at iiit!!
its just one, clean, slash. lightning claws have.....3 blades...1 slash=sword. whats the emperor holding?
well the theory on this is that when horus offered sag the opprotunity to join him, somehow he persuaded sag to join. the emperor emerged to see sag shaking horus's hand, and the emperor cut him down. sag, in his death, repented and it is THIS sorrow, and the outrage about learning the truth when they go into the little vision state, that causes the black rage among the blood angels.
as to why horus lowered his sheilds, he knew that the wolfies and dark angels were fast approuching (not ultramarines. word bearers did a good job in stalling the smurfs) and that he couldnt defeat the loyalists before they arrived, and when they arrived he knew he was beat. so he gambled, and lost. sux.
ANGRON, though is still alive and is still kickin butt and takin skulls! BFTBG!