rP22105 added a new structure for Gaul, a theatre (actually an assembly of princes).
rP23167 added art files for a carnyx and animations for an actor holding it.
D3331/rP24566 renamed the simulation template to assembly.
D3344/rP24597 tweaked the assembly's stats and enabled it.
rP24586 added an actor and icon for an unit using the carnyx.
The carnyx was a long, bronze, Celtic trumpet and used on the battlefield; its sound would intimidate opponents.
This patch introduces a trainable infantry champion for the carnyx-using actor, and adds a generic template (in case more trumpeters will be added for other civs in future patches, or mods), and an aura file, which lowers the attack damage of nearby enemy soldiers a bit.
While it has an aura that could make a difference, it has no training restrictions (unlike heroes); to compensate for that, it has a higher cost, less resistance, and less attack damage than other champions. If it turns out to make the Gauls too strong, its values can be adjusted in the future.
Having this (historically attested) unit would make the Gauls less similar to other civs.