Causal horns are the equivalent of light cones for the potential effect of an event on other events over time - promoting or inhibiting the probability of particular range of events.
They’re horns because they’re twistier than generalized cones (although they compose similarly toDavid Marr’s use of them). Anything from a simple cone via hooks and bulbs to corkscrews and nautilus shells.
A causal horn fits within slices of the light cones of a succession of information transmissions. It’s more information rich, slower, and multidirectional in comparison.