Briths are actually fairly capable of both, but are typically bipedal. Brith vikings/raiders are renowned for their incredible leg and arm strength as they are able to leap between different naval vessels with great dexterity. Out of combat though it's seen as bestial to be on all fours. 

A larger male brith can typically be around the size of an orc. So they can be pretty big in size, but are about as varied as humans in that category. 


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