SCP-073 appears to be a heavily-tanned male of Arabic or Middle Eastern descent in his early thirties, 185cm (6'1") tall and 75kg (165 lbs), with black hair and blue eyes. Arms, legs, spinal cord, and shoulder blades of the subject appear to have been replaced with artificial versions of unknown make and metal. Subject only takes notice of this when it is pointed out, and states that it has no knowledge of how, why, or when these replacements took place, stating it had had them as long as it could remember. There is a symbol engraved into the forehead of the subject, which appears to be of Sumerian origin. Symbol has of yet been untranslated, and subject appears distressed when the symbol is mentioned at all, refusing to speak on it. Subject does need to eat and drink on a regular basis, but is strictly carnivorous owing to its effect on plant-based items.

SCP-073, who refers to itself as "Cain", is generally polite and genial to all who speak to it, though it has been described as being cold and somewhat mechanical in its speech. It is very helpful, and enjoys aiding personnel in their daily actions, whatever they may be. It has highly detailed knowledge of ancient to recent events in history, and most commonly spoken languages in the world, including ones that have since died out. Subject has professed to having a photographic memory, remembering word-for-word all text in a eight-hundred-page dictionary that was flicked through in a minute and a half. It has scored above average in all intelligence tests given to it.

SCP-073's presence is inimical to any and all life grown in soil, causing death to any such life within a twenty (20) meter radius. Any land SCP-073 has walked on becomes barren within two (2) weeks and is then permanently unable to support life. Anything that is derived from soil-grown life, such as wood and paper, immediately rots and disintegrates upon touch of SCP-073. Further affected derivatives include anything hydroponically grown.

Violence directed towards SCP-073 reflects any damage inflicted on SCP-073 directly back onto the attacker, although SCP-073 visibly remains unharmed. This applies toanydamage directed at SCP-073. Attempts to get tissue and blood samples have proven futile: when the procedure was initiated, personnel carrying out the action felt the sensation of whatever was applied to SCP-073, and wound up with a sample of their own blood or tissue, despite the fact that ''all actions were directed solely at SCP-073''. Indirect damage through a medium also results in the person perpetrating the action receiving the wounds caused. Although SCP-073 receives no actual harm from damage to its person, it has stated that it still feels the pain of the action, and has politely asked researchers to abstain from overly harmful actions to its person.