Horus Heresy · atlas

006.M31 · The Isstvan Massacre · date approximate

Assault on Phaeton

Place: Phaeton · Segmentum Solar

Fig. 1 · Place on the map

Pyrrhic loyalist victory Legio Osedax is gutted, but the survivors take revenge; Phaeton holds.

At the dawn of the Heresy Kelbor-Hal remembered the insolence of Phaeton: forces of the Dark Mechanicum, disguised as merchant barges, hacked the noosphere of the forge world and invaded. The loyalist Legio Osedax (the “Cockatrices”) suffered extremely heavy losses defending its homeland, but the survivors later took cruel revenge.

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Loyalists

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Traitors

Special forces

Commanders

Type
Battle
Scale
2 of 5

Significance

The forge world — creator of the ubiquitous “Leman Russ” — held at the cost of Legio Osedax.

Disputed in the canon

  • The exact year is not fixed — the beginning of the Heresy. Kelbor-Hal’s personal revenge for Phaeton’s earlier “insolence”.

Sources

  1. Fandom: Phaeton
  2. Lexicanum: Phaeton
  3. Atlas compilation · source check 2026

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