The Hammer and the Anvil. Where a Cult Mechanicus maniple of the same forge world holds ground on a contested world, the two armies of the Omnissiah may muster as one. The Cult is the anvil — its slow, durable construct wall fixes the enemy in place — and the Skitarii are the hammer, the mobile gunline that manoeuvres behind that wall and falls on the flanks it shields. This is a campaign-only combined muster: neither gang joins the other's battle roster for good. Once both Mechanicus gangs hold ground on a world, in the local phase before the Endgame, they may field a single combined maniple, capped for that game alone, on a shared objective. When the battle ends the two forces part again, each to its own liturgy. Any Cult House may answer the call — the pact is sworn to the Machine God, not to a single named gang.
Alliances2
The Omnissiah's Requisition. The Adeptus Mechanicus are the Imperium's enginewrights, and where an Inquisition warband operates in the same region the Machine God lends the Throne its servants. In the local phase, once an allied Inquisition warband is present, the Skitarii maniple supplies a Tech-Priest Enginseer and a handful of gun-servitors — the weapon-mounted Servitor bodies — to serve as the Inquisitor's engine-seer and battle-escort. These units are drawn from this House's roster at battle time and returned when the fight ends; they are never kept, and no Mechanicus fighter joins the Inquisition's permanent gang list. The Mechanicus armoury is never copied into the Inquisition's book. This is the single agreed source of that support across the campaign — the requisition is offered here, on the maniple that answers directly to the forge, and nowhere else.