"The duty of the Emperor's defence does not end at the walls of the Imperial Palace. Our war is like an endless game of regicide, played over countless boards against infinite foes at once. In such a contest one must be constantly pre-emptive, always cunning and ever ready to seize any advantage that presents itself. Our gaze must rove far afield, and our every move must be perfectly executed. To do any less is to court final defeat."
The Aquilan Shield, known also as "The Gilded Guardians," are a Shield Host of the Adeptus Custodes, the stalwart guardians of the Emperor of Mankind. They are charged with the protection of those servants of the Emperor who bear great responsibilities or are destined for some unforeseen task or even martyrdom, which ultimately achieves some monumental objective in defence of the Throneworld of Terra in accordance with the unknowable holy vision of the God-Emperor.
Certain servants of the Emperor bear great responsibilities deemed directly relevant to the safety of Terra. Such esteemed figures are afforded the protection of the Aquilan Shield, at least until their usefulness is thought to be at its end. As the doomscryers of the Imperial Palace sift the tides of the empyrean for warnings of disaster, they also take note of those who - through example, thought or deed - are likely to avert such catastrophes before they threaten the Golden Throne. These fated individuals are honoured with the protection of the Aquilan Shield, for in this way a small band of Custodians can ensure a significant martial or spiritual asset survives to act in the Emperor's defence.
The Aquilan Shield are an informal brotherhood laced through the ranks of the Adeptus Custodes. They typically operate in small warrior bands, journeying across the stars to stand watch over their charges wherever they may be. No warning is given nor permission asked – the warriors of the Aquilan Shield appear as if from nowhere, avatars of the Emperor's will who announce their quarry to be under the protection of the Master of Mankind. Such an honour is beyond compare, and is never refused no matter the circumstances or the individual chosen.
The Aquilan Shield have acted as bodyguards to High Lords, Adepta Sororitas Canonesses, Lord Inquisitors, Astra Militarum Generals and Space Marine Captains. They have even protected two Imperial Crusade leaders bearing the title of Warmaster, staunchly ignoring the historic associations with he who first held that rank. Yet they have also appeared amidst flares of golden light to watch over firebrand frontline preachers, bewildered militia leaders and others of apparently little import. The only unifying factor amongst them all is that, while attending their duties beneath the gimlet gaze of the Emperor's own guards, these individuals are expected to achieve incredible things in the defence of the throneworld.
The Aquilan Shield fight to ensure such a future comes to pass, shielding their charges from harm until the exact moment the usefulness of the person under their protection is deemed spent. At that point they depart without a word, leaving those they guarded to look to their own defence. Tragedy often follows, but this is of no concern to the Aquilan Shield -- providing it does not jeopardise the safety of the Golden Throne.
- Codex: Adeptus Astartes (8th Edition), pp. 12, 24