"Borrel", known as "Varrel" (ヴァレル Vareru) in the Japanese version, is an archetype of DARK Dragon monsters used by Roken Kogami/Varis. The archetype is related to the "Rokket" archetype, which is also used by Varis.
With the exception of "Borrelcode Dragon" (which has more elements in common with Cyberse monsters rather than "Borrel" Dragon monsters), all "Borrel" monsters have a mechanical appearance, with gun barrels and revolver cylinders built into them, as well as having pieces of metal armor reminiscent of barrel shrouds.
The "Borrel" Link Monsters are mostly colored red and dark gray, whereas the non-Link "Borrel" Monsters also have an additional coloring based on their summoning method. Additionally, parts of the names of the non-Link "Borrel" monsters are an abbreviation of their respective summoning method.
In addition, each "Borrel" monster has a different wing color (except for the wingless "Borrelcode Dragon"): "Borreload Savage Dragon" and "Borreload Riot Dragon" share the same wing color as "Borreload Dragon", and "Borrelend Dragon" has the wings of multiple "Borrel" monsters.
Both the English and Japanese names of the archetype are wordplays on gun barrels.