The Or'es El'leath (Custodian)-class Battleship is an enormous Tau battleship that serves as part of the Tau Empire's Battlefleet, known as the Kor'or'vesh in the Tau Lexicon. Also an enormous carrier, it is capable of bringing three gunships as well as a large number of attack craft squadrons into combat to support the rest of a fleet. Early operational tests proved that like the other designs resulting from the Kor'or'vesh initiative, it met or exceeded all objectives required for its design. Despite the horrendous costs and resource expenditure involved in building these vessels, a number of Septs adopted the design and produced them in small numbers. For many tau'cyr these ships were held in reserve, and it was quite some time before knowledge of this vessel's existence became widespread beyond the Tau Empire.
Experience with the Gal'leath (Explorer)-class Battleship in combat, particularly against the Imperial incursion into sovereign Tau space during the Damocles Gulf Crusade, demonstrated a number of significant shortcomings that could not be overcome without a radical hull redesign, despite notable advances incorporated into the experimental Bor'kan variant of the venerable Gal'Leath. As the Kor'or'vesh initiative bore fruit with a progressively larger series of completely new and successful hull designs, it was only logical that the next step would be to produce a true battleship-class vessel -- that vessel would be the Or'es El'leath.
- A'rho - The A'hro was the first Or'es El'leath-class Battleship to ever be deployed in a military conflict for the Tau Empire, where it was first encountered by Imperial forces led by Admiral Kotto during the Taros Campaign. The “Custodian”-class and its attendant escorts were a complete surprise to the Imperial fleet there. Appreciating the threat this class represented, the battleship A'rho in particular was ruthlessly hunted down and destroyed by Admiral Kotto's fleet, but not before it served its purpose as a decoy by drawing off the Imperial fleet; allowing two Lar'shivre (Protector)-class Cruisers to wreak havoc on the Imperial supply convoys supporting the campaign.
- Firestar – The Firestar was a Custodian-class Battleship that served under Kor'O'Vanan's command in the defence of the Kel'shan Sept against the Tyranids of Hive Fleet Gorgon. Towards the end of the conflict in an engagement against the surviving Hive Ships, the Firestar was lured into an asteroid belt around Delmarra and was irreparably damaged.
- Rysm'Ca'Vas – The Rysm'Ca'Vas, which roughly translated means the “Shield of Purpose” in Low Gothic, is a Custodian-class Battleship that served alongside its sister ship, the V'os U'kysa, during the raid on the Imperial world of Typha-IV. Both the Rysm'Ca'Vas and V'os U'kysa were modified to be stealth ships for the raid, and had most of their armament stripped and their Gravitic Hooks removed in order to fit additional cargo and life support pods to extend their range and transport capacity. They successfully deployed their forces without detection on Typha-IV during the mission, and waited out the conflict out of system until extraction, where they then picked up the remaining Tau forces and returned back to the Tau Empire.
- V'os U'kysa – The V'os U'kysa, which roughly translated means the “Spear of Unity” in Low Gothic, is a Custodian-class Battleship that served alongside its sister ship, the Rysm'Ca'Vas, during the raid on Typha-IV.
All Custodian-class Battleships, as standard, are armed and equipped with a set of both port and starboard Railgun and Ion Cannon batteries, a prow-mounted Gravitic Launcher and Deflector Shield, port and starboard launch bays each capable of holding up to three squadrons of Barracudas and Mantas, four defensive turrets mounted around their hulls, standard Tau ship gravitic shielding, and advanced integrated tracking systems like those of the Skether'qan (Messenger)-class Starship. These systems consist of highly advanced data storage and processing facilities to cope with the vast amounts of information they carry. When linked to the ship's sensors, this processing power can be used to provide a direct feed to any nearby ships' turrets to improve their accuracy and effectiveness. Custodian-class Battleships also feature a set of Gravitic Hooks enclosed in a single, shrouded, hangar-type enclosure specifically designed to hold up to three Kir'la (Warden)-class Gunships which the Custodian can carry into battle.
- Battlefleet Gothic 2010 Compendium, pp. 159-160
- Codex: Tyranids (5th Edition), pg. 21
- Imperial Armour Volume Three - The Taros Campaign, pp. 212-213
- Tactica Aeronautica, pp. 43-44, 69-70