A dreadnought is a gigaparsec-long or larger spacetime battle vessel used by some civilizations, constructed from compacted universal membranes and equipped with finite- or infinite-ranged weapons systems to attack -verses, SAW gliders, cosmic entities, and opposing metaspace vessels. Dreadnoughts are a type of large-scale alternative to combat at multiversal and larger scales, intended to counter tactics such as dimensional mine blockades, Planck-scale construct swarms, and dormant berserkers.
The reasons for constructing a dreadnought - or a fleet of them - are highly variable. They can be useful as storage and defense mechanisms for valuable information or computers, especially for civilizations that find it difficult to stay in one place. The threat of a dreadnought attack can also be a powerful bargaining chip in negotiations with weaker polities or in wars with larger ones.
Many regions of the omniverse have polities with similar mental structures allowing for collective agreements on regulation of dreadnought warfare as a means of dispute resolution; other regions only tend to see them used occasionally, as they have weaknesses to many higher-tier techniques and weapons.
A dreadnought is essentially a massively fortified launchverse guarded by hundreds, thousands, or millions of nested universal boundaries that continually fold and ripple into and out of one another in higher dimensions. From the outside, they have the appearance of long, amorphous amoebae or worms, though some can be seen taking radially symmetric shapes like plankton or more rigidly organized shapes like the conventional spacecraft used by smaller polities. While normally configured not to interact with electromagnetism, when visible, dreadnoughts can display any physically practical arrangement of colors and spectra.
Much like an exophage, a dreadnought moves with its surface, though dreadnoughts tend to roll along the multiversal fabric much like hovercraft instead of merely pulling themselves along. Some are equipped with specialized modules for propulsion in alternate regions; rift turbines in the Rifters' Realm, for example.
A dreadnought's defense begins far from its surface; most have modules to alter the metaspace around them in various ways, such as creating arrays of topological defects to render continuous motion near them impossible or flooding extrauniversal space with storms of remotely-controlled or autonomous kugelblitz-based drones as an electromagnetic defense. Many are also equipped with temporal disruptors along their membrane, converting one spacetime medium inside into a different one in extrauniversal space, and slowing down incoming weapons to the point of unusability or shunting them out of the timeline altogether. Often, simply being a finite distance away from a dreadnought poses a tremendous risk to anything that isn't a comparably powerful dreadnought or cosmic entity.
Universal boundaries, which essentially form a dreadnought's main belt of armor, are impervious to most forces and will not let particles through unless a hole is bored into them somehow. In addition to this, universes with hostile laws of physics can be chosen for such an armor belt; for example, a membrane that instantly reflects all bosons can be useful as an auxiliary defense, and one that dumps energy outwards can serve as a radiator or area-of-effect weapon. As most dreadnoughts possess enough of these barriers that all of these effects can be applied simultaneously, their "main belt" is practically invulnerable to effects below their scale.
As the inside of a dreadnought can often be largely composed of ideal computing substrate, with physics altered so as to maximize time for the defender to react, trying to breach into one is rarely a good idea. Even the use of portals to attempt to circumvent dreadnought defenses is rarely successful, as inbound portal connections usually find themselves terminated when the dimensional structure on the other side is promptly adjusted so as to make connection impossible.
The unfathomable destructive potential of a dreadnought's defensive arrays can very easily be turned into its greatest weapon. When optimized for attack, dreadnought passive defenses can wipe out arbitrarily large regions of a multiverse by simply being present, to say nothing of active defenses. Incompatible geometries, destruction of bosons, and even induced Big Crunch or crossover events can be among their more potent weapons.
Impact with a dreadnought is usually entirely lethal for the other party, and dreadnoughts use this advantage frequently, accelerating to high speed and sweeping out vast swathes of opponents by simply slamming through them. Often, in doing so, the dreadnoughts promptly pick up mass-energy and more universal membranes from the objects they hit, actually fortifying their defenses further rather than wearing them down.
Some dreadnoughts are loaded heavily with informational and memetic weaponry, which can prove helpful against cosmic entities or opposing civilizations that prove too troublesome for a standard physical approach. Given that they have enough computational power to overwhelm even vast multi-universal civilizations, they are exceptional at developing new techniques on the fly against opponents whose mental structures are unknown to them.
As auxiliary measures to all of these, dreadnoughts designed for combat against one another carry slightly more conventional weapons, generally of the sort that fire concentrated packets of annihilating manifolds or highly reactive universal membrane material. Others fire weaponized SAW gliders or other infinite-speed projectiles for combat at longer ranges. These can be likened to the batteries of naval artillery aboard sea warships, which, while perhaps specialized and fading out of utility, maintain a legacy of ship-to-ship combat that many polities prefer to re-enact.
The role of dreadnoughts in multiversal warfare varies wildly depending on omniversal location, and military doctrine is as diverse as the polities that enact it. Nonetheless, among the civilizations that have adopted dreadnoughts, some patterns have been observed.
One common approach is to use them as a first-strike weapon, hiding them away in pocket multiverses until their use is necessary and then unleashing them as fast as possible when conflict is imminent. Combat between dreadnoughts used like this is fast-paced and usually massively destructive in terms of collateral damage, as they can make arbitrarily many passes by each other in very short timeframes and wipe out swathes of universes as they move and engage one another. Superintelligences directing dreadnought warfare are often wired to think independently of time, so as to be able to keep up with an infinitude of actions occurring faster and faster.
In regions that call themselves more "civilized", dreadnoughts are kept to low speeds and used like conventional naval vessels, engaging in broadside duels individually or in fleets and often only fighting until one flees. Treaties regulating size, offensive and defensive capability, and speed can keep these battles from becoming too costly, and there exist backup measures to ensure that a civilization that breaks the rules is put down quickly.
There exists a natural tendency to upscale dreadnoughts over time, from gigaparsecs and thousands of universal membranes up through petaparsecs and billions, or of course even higher; a larger one is almost universally superior to a smaller one, and although fleets of dreadnoughts can level the playing field slightly, the arms race tends to leave them behind. Of course, material limitations, political agreements, and countless other factors can prevent this from occurring.