Mars Walsh is a little bit crazy. She really does live up to her Vort title she makes guns, Nohaa Tahh'chackt Bahh. While she was also a little prodigy like Gordon Freeman, and is only slightly younger than him, she grew up in a home where guns were the norm, and where she had easy access to some of the best educational facilities in the country. Graduating high school at 16 and already attending classes at UCSD, she got through undergraduate classes in Medicine by the time she decided to change majors and go for Forensics instead. At 24 she was working with San Diego police as a forensics and ballistics expert, and very shortly was brought on board at Black Mesa for their own weapons research in New Mexico.

Marciella enjoys anything that explodes, and if she can put holes in something with them, even more so. When the Resonance Cascade occurred at Black Mesa, she was the head of the Ballistics and Experimental Weaponry department. In the time that she'd been working at Black Mesa, however, she'd also already gotten a reputation among other more stuffed-shirt scientists as 'hard to handle' and 'too headstrong'. Read: she was a woman in a man's profession and they weren't having any of it. It was also those qualities which got her 'sent to the head office' more than a few times.

That head office happened to be of the Human Resources director. That would be, eventually, Keenan Lane. Was she ever chastised for being too difficult and not willing to work under the men who - in her words - stagnated the weapons development team? No, not in the slightest. Did she come out of the office a bit rumpled and sometimes slightly drunk? Often. Not quite often enough to turn heads, thankfully.

Because she lived in the dorms on-site, Mars had relatively easy access to a good number of Black Mesa amenities: the pool, lunch and dinner restaurants, laundry, shooting range, pub. She became bored of those things almost instantly (aside from the pub and of course she never tired of the shooting range!), and since her hyperactive brain rarely allowed her body to rest, Mars began exploring the facility after-hours. Because she had clearance, it was never really noticed - she had top-level access to almost every section of the place already. And those places she didn't? She used her small size and incredible agility to her advantage. She also pioneered the use of certain types of armor: she swiped Armacham's Icarus suits almost whole the moment she saw them at a trade show. Because they allow the user to not only withstand a considerable amount of damage if struck by anything, but also they can turn nearly completely invisible and cling to surfaces like ceilings, walls, air vents, and even moving fan blades.

Early on in her exploration of the facility, however, she learned that she wasn't the only one prowling about at midnight or the wee hours. More than once, she'd seen a shadowy figure slowly traversing dim hallways. When she realized that figure was tracking her movement as well, rather than giving up on the whole exploration venture, she decided to just use the best tactic she knew - and introduced herself to Lane as he surveyed one of the toxin processing vats below. He has always appeared to tolerate - even welcome - her behavior, acting bemused at worst, and highly entertained at best. Though he might complain that she steals his liquor and winds up passed out in the corner, the fact that she did so in his Vortally-created office while he wasn't there impressed him far more than angered him.

That's right: Mars Walsh broke into his office - the office with no doors. The office which he constructed Vortally and doesn't physically exist anywhere on any Earth. Like Geoff, Mars's mind is all but impervious to Lane's telepathic nudges or exploration. But she doesn't actively know that, it's merely an effect her high-ranking latency with Vortessence conveys. Her aura can hardly be seen, only those who know that it is there can even really sense it. Looking at her aura, so Lane claims, is like "looking at a black-velvet painting, that's also using black paint." The only sure way of noticing it seems to be by placing her between the viewer and a brighter aura. Since the defeat of Ulathoi and the subsequent reconstruction of Earth, she's delighted in the use of that very feature, testing herself against any given Vortally-skilled opponents.

In the years before the Resonance Cascade, Mars had begun effectively embezzling funds to aid her personal works. Lane knew all about them, of course; when he replaced Lawrence Manning as the HR head, that gave him considerably more freedom in allowing her to even hire new employees that actually worked on her excavation. The weapons lab and armor research areas she'd comandeered before now had an exit that was not on any Black Mesa blueprints. She'd designed it, and funded most of it from her personal patent earnings, but when it was nearly completed (a tunnel wide enough for the two stolen Black Mesa SUVs packed with survival gear, weapons, armor and eventually people) it was also nearly discovered by a well-meaning but not-trusted financial advisor. Lane had to pull a lot of strings - as well as delete a lot of video feed, and wipe a lot of memories - to make sure that didn't happen again. But he not only tolerated this behavior, he encouraged it. Her 'stick it to the man' attitude is something that perhaps her time in the Police department might explain, though it's never really been too clear. Having someone like Keenan Lane on 'her side' meant that she had almost carte-blanche spending habits.

Toward the end, nearer the Events, she had made more than passing friends with several of those scientists who wound up over in the Anomalous Materials lab: Gordon Freeman, Barney Calhoun, Izzy Kleiner, and Arne Magnusson. Magnusson in particular was of interest to the young woman because he, like her, really really enjoyed rockets, explosions and go-booms of all sorts. In researching for her ballistic works, she often consulted with the gruff man, and equally often wound up putting all manner of expressions on his face. She loved to poke at him with completely inappropriate innuendo, off-color remarks, and even leaving extremely compromising pictures on his computer desktop... Usually right before a big meeting or a tour group arrival.

After the Events, Mars played a huge role in the continued survival of the Black Mesa refugees. Her knowledge and expertise in weapons and the layout of the structure itself allowed them to find stray survivors (and some that hadn't survived), as well as being able to pick through the difficult collapsed hallways to find supplies. She helped train many of the newcomers in safety and hunting, provided any gun-handling training needed, and got to put her own knowledge and skills to the test. Once Lane and the other Pantheon members began coming to Black Mesa again, and their plans to not only hit up Europe as a rescue operation but to make sure that Ulathoi was well-watched, Mars remembered how much she liked hanging out with utterly inappropriate people.

She seems blissfully ignorant of the damage that Wilson might do to her - she's "barely the mass of one of his legs" (it's true) and he's rather intensly stronger than he looks (and he looks damnably strong). It was purely his hesitation that eventually led to her winding up pregnant with Lane's son Nohaa - she watches the pair of men with amusement as they bat insults back and forth about 'who got who first'. Of almost all the people that Melissa has approached about this sort of thing, Mars is actually quite amenable to "being bred" by her. However, while she prefers the 'good old-fashioned way' of getting there, Mars didn't actually give birth to any of her other children after Nohaa. That was handled by healthy volunteers: once more showing a huge difference in the culture between their world and that of Primal Earth.

Mars enjoys looking - and feeling - young and healthy. Taking Hoyle's lead, she expressed interest in the whole idea behind having a stock of cloned bodies for either partial or full replacement use. In her case, however, because she was subsequently told of how strong her Vortal latency was, Mars decided to have all her clones outfitted with the Icarus process. Making them stronger, lighter, faster, and moreover: able to do things that her original 'born' body could never hope to do. Though she hardly uses the abilities, because she's more apt to concentrate on 'what she already knows how to do', Mars does have borderline empathy, a loud but short-range Vortal 'voice', and has the extremely unusual ability of being able to open up other people's Vortal constructions. She's always been able to do that, but now she can do it on purpose.