The Magos' Reliquary is a fortified machine-shrine of armoured bulkheads and sealed relic-vaults — dense enough to break line of sight, strong enough to stand a siege.
A fighter inside the Magos' Reliquary, in base contact with its interior, counts as being in full cover against all ranged attacks. A friendly Tech-Priest inside the Reliquary may work its Rites of Repair on any friendly CONSTRUCT within 6" rather than only an adjacent one, the liturgy amplified through the shrine's resonant vaults.