Forgeworld today has let go of more Mechanicum models set for pre-order today. Myrmidon Secutors already have rules for them in the Horus Heresy Book 2; Massacre.
You can see more by following the link below to Forgeworld.
Myrmidon Secutors excel at the art of destruction and the embodiment of that power within their own vastly augmented bodies. To them war is a matter of cold logic and murderous equation, and they have at their disposal a deadly arsenal of ranged and close assault weaponry, including graviton guns and phased plasma-fusils. When used in combination with their energy-wreathed power axes, they are terrifying force for any foe to reckon with.
The Mechanicum Myrmidon Secutors set, designed by Mark Bedford, comprises three resin models and is available to pre-order now. These sets will be despatched from Monday 31st March.