So long as the Senate watches over her, Archadia's well-being will ever be assured.Chairman Gregoroth
The Imperial Senate is the main legislative body of the Archadian Empire in Final Fantasy XII. 200 years before the start of the game, the Senate was actively engaged in the rule of Archadia before the rising power of the military caused a turn towards an imperial system.
Because of the loss of its powers, the Senate is usually hostile to the Emperor and House Solidor in general. However, since it does not command any significant military force, it can do nothing more than scheming against the Head of State using its (limited) powers.
While formally retaining legislative powers, the Senate cannot pass legislation without the emperor assent and its function are thus merely advisory. However, it would appear that the Senate still holds some power of scrutiny over Archadian public officials, since in 706 Old Valendian the Senate forces Emperor Gramis to dismiss Vayne Solidor from the post of Consul of Rabanastre and to recall him to Archades to stand trial for his misuse of the military.
While confronting the Senate, Emperor Gramis also states that he must "make a choice" between his throne and his son. This might mean that the Senate has the power to empeach and remove the Emperor, should he damage the State through his actions.
The Senate fears the rising strength of the young and ambitious heir to House Solidor, Vayne, and so moves to have him dismissed from his post of Consul of Rabanastre and recalled to Archades, citing the loss of the 8th Fleet of the Imperial Army; once in Archades, Vayne is to stand trial for his misuse of the Archadian Army and be excluded from the line of succession. In his place the Senate hopes to prop up the child Larsa. Vayne comes to Archades to confront his father, Emperor Gramis, but finds that the elderly and sickly emperor also prefers Larsa.
Unwilling to step aside, Vayne destroys his enemies in a single move: he kills his father and then blames the crime on the Chairman of the Senate Gregoroth, who is executed (although it is later claimed that he commited suicide). The Ministry of Law subsequently proclaims a state of emergency and appoints Vayne as "temporary" Autocrat: with his new powers, Vayne dissolves the Senate and has his members put under arrest, encountering only limited resistance. Judge Drace alone attempts to stop the coup d'etat, but she is executed on the spot by Judge Gabranth under Vayne's orders.
According to the memories of Marquis Halim Ondore IV, the coup is a shock for the Archadian society, but is strongly supported by the Archadian Military
The further fate of the Senate is never revealed, and it is unknown if the body was ever restored.