Oshu is First Prime of the Goa'uld System Lord Yu.
Oshu might be a physically small man, but he makes an impressive First Prime for his master, System Lord Yu. His master is one of the oldest of the Goa'uld and is showing signs of "old age"—he cannot take a new host and the sarcophagus is losing its effect. Slowly, but surely, Yu is going senile.
Oshu speaks for his master with authority, however Yu gets mad at him a lot because of it. Oshu is never quite sure when he should speak for his master or not. Lord Yu has even threatened to kill Oshu for speaking to him as if he didn't know what was going on (even when that was truly the case).
When Anubis was bound to find the Lost City of the Ancients to obtain the weapons there, the SGC devised a plan to entrap him. The plan was to have the Tok'ra plant a fake tablet which would lead Anubis to Vis Uban, where the SGC would take out his enhanced weapon powered by his collection of "eyes"—including the Eye of Ra he obtained from Abydos and used to destroy that planet. Because Yu was the only System Lord who did not vote to have Anubis reenstated among the System Lords, Teal'c went to him to lead the System Lords to complete the attack on Anubis while at the planet. System Lord Yu agreed to do so, and Oshu went about implementing the plan to assemble his fleet and then make the attack.
But, while Teal'c and Oshu were working on carrying out the attack plans, Lord Yu had them divert the fleet to a location far from where the attack was to take place. Oshu then placed Teal'c under arrest. When they were alone, Oshu explained to Teal'c that he knew that Lord Yu was not a god and that he was losing his senses, but he still remained loyal to him. Together, Teal'c and Oshu contacted Ba'al to work out an attack plan with the other System Lords, with Oshu speaking in his master's name and saying that Yu's fleet would follow him because they were after the same goal: to reduce Anubis' power or to eliminate him entirely.
Oshu led the fleet for Yu and joined the other System Lords at Kelowna, where Anubis had gone in order to obtain the secrets of naquadria. Anubis' large ship was destroyed, but, unknown at the time, Anubis escaped. It did not appear that there was a significant loss among the attacking System Lords, as we don't hear of any of them being destroyed in this battle.
After Earth was successful in using the weapons of the Ancients stored in an outpost in the Antarctic to destroy a large part of Anubis' fleet, and presumably Anubis, the remaining System Lords wished to enlist the help of the SGC in reestablishing the power balance among them. Ba'al had taken more of Anubis' remaining planets, ships, and weapons than what the System Lords had agreed to. So, the System Lords, represented by Lord Yu, Camulus, and Amaterasu, went to the SGC to negotiate. During these negotiations, Oshu spoke for his master, standing behind him all the while. Lord Yu was the only System Lord who brought someone to accompany him to these negotiations.
When the System Lords sent a ship to attack Earth while the negotiations were going on, Dr. Elizabeth Weir, now in charge of the SGC, had the three System Lords and Oshu confined as prisoners of war. Oshu made a passionate plea for his release, stating that he would die before revealing any information and that he would be of more use to Earth if he were able to fight with honor against Ba'al. Again, Oshu showed great strength and loyalty and Dr. Weir gained his respect when she let all of them go because she knew that they would not be able to gain information from them and that they indeed would be of more help if they were out there fighting the battles.
--DeeKayP 18:55, 20 Jun 2004 (PDT)