The Order of Secrets
Durable Body is the physical manifestation of the Enduring Form skill. To the point it actually is ‘free’ on all modern Catalysts as long as you have that skill. If you lack the skill it provides 1 point of bonus Physical Stress as if you had a single rank of the skill and uses one Sequence slot.
While the physical manifestation could look like anything from a glowing nimbus of light to a Space Suit, usually Durable Body simply looks like clothing of some sort.