Legend
Hestia, more formally known by the ship designation
Interstellar Travel-Purpose Cosmo-Reactor Vessel Hestia, was one of the Twelve Machine Gods of the Atlantean pantheon, and, subsequently, one of the twelve Olympians of the Greek pantheon. Her original purpose within the Alethian fleet was, as her designation implies, a power generator and distributor, a role she continued to play as Greek goddess of the hearth, the right ordering of domesticity, the family, the home, and the state.
Although she is a member of the twelve Olympians (being simultaneously its eldest and youngest member by virtue of being the first-born of Cronus while also being the last one he spits out), Hestia plays a notably small role in Greek mythology. However, this should not lead one to dismiss her as being any less important than her siblings. Without the Cosmo-Reactor Vessel and its limitless supply of energy, the Alethian fleet would have run out of power long before they set their scanners on planet Earth, or even before they breached the Tannhäuser Boundary. Without Hestia to assure the integrity of the sacrificial rites, the Olympians would have rapidly decayed into lesser nature spirits after being defeated by the White Titan. Without Hestia, western civilization as we know it would not exist.
Personality
Likes: Camping, the content smiles of people who eat her cooking
Dislikes: Unclogging toilets, public displays of affection
Talents: Housework, fading into the background
Natural Enemy: Aphrodite,
Chiyou
A prim, proper, and perfectly professional maid-type Servant. She holds affection for everyone, and so tries to serve them in a pleasing manner. However, precisely because she tries to cater to everyone's interests, she must keep them all at a distance. Hence, the vow of virginity.
Hestia has no desire for the Grail, for one simple reason:
she renders it obsolete. If one were to think of Holy Grails as "omnipotent wish-granting machines", then Hestia, who can produce an endless amount of magical energy for the purposes of fulfilling her Master's wishes, can also be called a "Holy Grail". Masters who summon her, therefore, are considered to have won the Holy Grail War without spilling a single drop of blood. However, this does beg the question of why Hestia would allow herself to be summoned as a Heroic Spirit in the first place. The answer is similarly simple: Hestia is the goddess of bringing people together. The Holy Grail, as an object that also brings people together, is thus within her domain, and its ability to gather personalities from every time and place is within her interests.