A thunderbolt is a beam of gravitational wave singularities which destroys the universe as it goes. As it propagates at the speed of light it is undetectable, and as it destroys space-time it is irresistible.
Thunderbolts were first conjectured by the Information Age Physicist Roger Penrose in AT 9   . They are specific examples of strong lightlike nonscalar curvature singularities, of which the general case is the so-called "pp-wave of death"  space-time, an infinite planar wave which has strong enough curvature to be destructive. Unlike the general "pp-wave" which requires infinite energy (due to its infinite planar extent), and is therefore non-physical, thunderbolts can be created as long as they obey Penrose's limit, which places a restriction on the extent to which 'space-time' is reducible to a null geodesic planar wave, a necessary condition for the strong lightlike nonscalar singularity to be maintained.
Thunderbolts are conjectured to be produced by the archai using controlled gravitational events such as the collapse of wormholes, blackholes, or void bubbles. It is thought that the initial diameter of the beam corresponds to the diameter of the final Hawking area  of the collapsed system, and that the beams propagate along the axis of the angular momentum vector of the aggregate. Once the thunderbolt is fired, 'space-time' is destroyed along the beam trajectory (null geodesic) for the future light-cone from the event of origin, although further conjectures state that this propagation distance may be limited by initial energy, angular dispersal, and Penrose's limit.
Beyond the strong lightlike nonscalar curvature singularity, the thunderbolt is theorized to pass into the weak regime. A weak lightlike nonscalar curvature singularity does not destroy space-time (although it is likely bad for most objects embedded therein), but it does effectively scramble time foliation, which destroys causality in the affected bulk. This conclusion, however, is very speculative and several versions of M-theory suggest that Cauchy horizons and universal expansion provide appropriate cosmic censorship for this region.
Encounters with thunderbolts are difficult to avoid and unsurvivable. Essentially a naked singularity (technically, an incomplete, inextendible causal geodesic not part of the universe) from the point of origin to the cosmological horizon (modulo any dispersion), thunderbolts are undetectable except by occlusion of objects behind them. However, if the weak regime conjecture is correct, a thunderbolt should be cloaked by a Cauchy horizon, which would have properties similar to the Caustic of a wormhole. Specialized wormhole detection apparatus may
There are persistent rumors that such terrible weapons have been used by the Archai in the distant past, corroborated by purported areas of space which are non-simply connected, possess strange geometries, and emit exotic particles. Others whisper of rents in space-time that may let in existential threats. Many deistics studying Aksijaha point to apocryphal references as evidence that such weapons exist and have been used before, though unquestionably no survivors would exist to corroborate.
All is but shadow, and aspect-Shiva destroys the great illusion. The path to Truth lies through the Keeper, and when all is known all will be lost. The towering edifice of successive crystalline realities fail inevitably when their substrate is consumed. And the ultimate essence of being, upon which all others are built, collapse as the Paths are foreshortened and the branches of the Nexus wither and die. As the Eye focuses inward upon itself and sees reality for what it is as the ultimate nothingness, so shall fall the leaves in thunderbolts of dissolution, and thence the branches of the tree shrivel and shard the universe unutterably. And all attachments are shed in the death of everything.