Latio is the current head of the Crudelis family, one of the Six Sources of Atlas equivalent to the Lords of the Clock Tower. Her family was involved in the creation of Ergo, and she now seeks to obtain him as her inheritance.
The Adventures of Lord El-Melloi II
The Man Who Devoured God
The Devil of the Wandering Sea
Latio visits Reines El-Melloi Archisorte, wishing to cooperate despite Reines being the sister of her enemy. She explains to Reines about Ergo and the three gods inside of him, and how there is currently a Divine Body - an organ of a god - from one of Ergo's three gods in Japan. Latio requests that Reines take data from the Divine Body's owner in exchange for Latio sharing the analysis results. Latio needs that data to obtain Ergo and Reines needs it to save him, so they can cooperate until the analysis results are shared.
Reines, Latio, and Luvia traveled to Egypt to meet up with El-Melloi II's group, where Latio would remain an ally until El-Melloi II delivered information on Ōkuninushi, the god of the Yakou Divine Body. As El-Melloi II's group was boarding their plane in Tokyo, Reines called him to inform him that while investigating the Wandering Sea her group had come across a locked-door murder mystery, with the victim being a pharaoh.
Latio is an Atlas alchemist, meaning she is constantly using Thought Acceleration and Memory Partition to estimate the future a few seconds ahead. Aside from that, she can fight using alchemy that employs her own bones as catalysts. The Six Sources of Atlas are a title for families of long-standing tradition, which in the Crudelis family's case, is the use of their own bones as Exoforms, similarly to how the Eltnam family employs their own nerves as Etherlites.
Her familiars are monsters made of bone, taking multiple forms including spiders, wolves, and bird skeletons that ignore the laws of physics to be able to fly. Lord El-Melloi II's magical bullet aren't enough to make the familiars tremble. Judging by the capabilities of each individual familiar, Latio's overall war potential is confidently assumed to surpass any modern day general. Although Spiritual Evocation also has developed the skill to use human bones as familiars, Latio's version is another category of skill, not only due to being different in both quality and complexity, but also due to not using any kind of departed soul.
And a particularly powerful member of these monsters is a bone giant named Tangere, measuring above 2 meters in height and weighting close to 200kg. 2 of Latio's Memory Partitions are allocated to him, enabling him to speak with an overly masculine voice. Quoting Latio, "allowing him to develop by his own judgement resulted in this degrading personality". To save magical energy, he usually takes the form of a normal-sized skull. Aside from combat, he's also capable of analysis and inspection, being able to simultaneously compared multiple categories of mythology and magecraft.
Tangere's high combat capabilities are mainly defined by high defensive and regenerative abilities coupled with estimating the future, allowing him to counter attacks he never seen before "as if he knew they were coming". For instance, Gray's Battering Ram, which is equivalent to a Servant's D-Rank Mana Burst Skill and able to smash a tank's armor, sent him flying without crushing him; and Rin Tohsaka, one of the most powerful modern mages in terms of raw damage, managed to pierce his head with a fully chanted Jewel Magecraft spell capable of killing Heracles once, but he took the hit without collapsing and regenerated in an instant.
Additionally, something of the same nature as the bone familiars could be used mend the aged, collapsing hull of a ship and sail it without a proper crew. When operated this way, the hull is fortified enough to take a hit from a rocket launcher without being damaged or pushed. Although the mechanism is decidedly less powerful than Tangere, it utilizes a similar logic to defend the hull.
Instead of fully relying on her familiars for combat, Latio also partakes in close-ranged combat using a bone sword. She directly manipulates the bones inside her body to perform a sequence of superhuman jumps, all while estimating the opponent's dodge trajectories with Thought Acceleration and Memory Partition.
Incidentally, the Atlas Institute has a rule forbidding weapons created inside the Pit from being taken outside, but the Exoforms are merely bones, not counting as weapons. For that reason, she was able to overwhelm Gray, Rin Tohsaka, and Ergo in a 3-on-1 fight without infringing Atlas' regulations.