Caliban

the destruction of Caliban
After the Horus Heresy, Lion El'Jonson and theDark Angels fleet returned to Caliban, he and his fleet were immediately fired upon by the orbital guns. Puzzled, El'Jonson withdrew. when he learned what happened, El'Jonson fell into a terrible rage. He had gone from one point in the universe to the next, clearing away traitors and demons, when he finds that his own planet had fallen to the Ruinous powers. El'Jonson's fleet bombed the planet and destroyed the orbital guns. El'Jonson then led a strike force into the Tower of Angels and dueled his former friend. They were equally matched, but finally, Luther keeled over in exhaustion, leaving him open to a deathblow. El'Jonson couldn't bring himself to kill his former friend and so, Luther lashed out with a psychic attack. As Luther saw his oldest friend dying, his mind cleared and he forced back fell to his knees, sending out a cry for help in the Warp. The Chaos gods, angered that they had lost such a valuable person, caused a great warp rift near Caliban.

The Dark Angel space fleet also bombarded the planet mercilessly, and this caused the structure of the planet to collapse. The bombardment, combined with the newly formed warp rift, broke the planet up and it is now an asteroid field. The largest piece, which survived due to the massive void shields in operation around the largest fortress-monastery, called the Tower of Angels, was hollowed out and became a gigantic battlebarge which is now the home of the Dark Angels. This ship is known simply as The Rock. When the Dark Angels searched the Tower, they found Luther, babbling incoherently, but their Primarch was no where to be seen.