Although automated machines of war were forbidden in core Domain space, war drones were quietly employed outside of officially incorporated volume. Frontier garrisons were often bolstered by drone ships, and they were deployed liberally against rebellious worlds to tip the terrible balance of attrition, setting the industrial might of the Domain versus the lives of 'freedom fighters'.
There are elements of standard droneships within the hull structure, but they are covered by malevolently angled glacises and illogical tangles of conduit. Surely this monstrous vessel is the product of some deranged Domain naval architect, or a production chip corrupted by exposure to kilolights of faulty drive field?
The Guardian is a derelict battleship found defending the Domain-era Cryosleepers. Due to the fact only 2 Cryosleepers generate per Sector seed, only 2 Guardians can ever exist in the sector, and for a very good reason. Like all Derelict and Remnant ships, this ship is hidden in the Codex, and is unboardable.
This ship has a little less armor than an Onslaught, but is faster, more maneuverable, has a much bigger flux capacity, and has more frontal weapon slots, which makes it capable of projecting a truly humongous amount of frontal firepower. It's also nearly as big as the Onslaught.
The main weak point of the Guardian is its little-defended (by comparison) rear section, which has a single large mount. A fast, maneuverable and heavily armed ship like an Aurora can get behind it and quickly disable its engines. If the Guardian is unable to aim its frontal guns at its enemies, it will be easy prey to a group of smaller ships and quickly destroyed.
A straight, head-on fight with an Onslaught or a Paragon will be devastating to a Guardian. An Onslaught's intense arsenal will quickly tear through a Guardian's armor and destroy it, while receiving little to no damage. And that's without mentioning how lethal an Astral can be to it.
Although it won't win in a straight fight with either of the above ships, it's an extremely serious threat to all ships, being capable of quickly destroying them if they get too close, and with the enhanced range it has thanks to its Advanced Targeting Core, this ship can fire weapons like the Gauss Cannon at several thousand SUs of distance.
The Guardian is extremely fast and maneuverable for a ship of its size, and its Plasma Jets make it even more of a speed devil, fortunately, they have a relatively long cooldown of a little less than 10 seconds.
The Guardian has a final, nasty trick in its mechanical sleeves: It has a hidden modifier known as "missile_reload", allowing it to passively regenerate its missile ammo, at no cost, with no disadvantages. In other words, it will never permanently run out of ammo, allowing it to keep firing its missiles for the entire battle.
Trying to outlast a Guardian (keep fighting until its peak performance timer ends and its CR drops to zero) is not an option. Due to how long it can maintain its peak performance, it's far more likely that the opposite will happen.