Zigara, designated P7K-135 by the Tau'ri, was the home to a near-Human species called the Zigarans and was once one of Marduk's treasure planets. After Marduk was overthrown, the Zigarans came to realise that their god was a fake and buried their Stargate, cutting themselves off from outside contact. Thousands of years later, the reactivation of their gate brought them to the attention of the Goa'uld Bel.
History
Fall of Marduk
Zigara first came to the attention of Marduk as it contained large natural deposits of naquadah, gold, as well as the various gems and crystals used in all Goa'uld technology, and the Goa'uld used the world as a treasure planet.
However, after Marduk's first apparant death, when he was overthrown by his own priests, one of his underlords known as Sarconic attempted to claim Zigara for his own; he claimed he was acting on behalf of Marduk himself as the native Zigarans had not at that time heard of Marduk's downfall. The local priests were suspicious of this so-called messenger of god, however, especially as Marduk had a habit of appearing to his people directly through ring transporters and so they attempted to confirm his story by contacting the priesthood on Marduk's "home office" and soon discovered the true fate of their "god". Shocked that Marduk had been so easily captured by his own priests, this lead them to the conclusion that they had long whispered; the Goa'uld were not gods. The priests would secretly spread this among the people, inciting a full-scale rebellion against Sarconis; they reasoned that, if Marduk had not been a god, then his messenger was even less worthy to hold claim over them.
A short-lived battle resulted in the death of Sarconis and many Jaffa who were still loyal to Marduk. The Zigarans decided to bury their Stargate and simply awaited what they thought would be the inevitable retaliation from space; this would never come, however, as Marduk had kept the addresses of his most prized planets entirely secret to all but his most trusted underlords. After about two generations of this seeming neglect by the Goa'uld, the people believed they had seen the last of the System Lords and so turned to reconstructing their lives without their god to control their lives.
Re-emergence
Thousands of years passed, the Zigarans slowly losing the truth about what once happened to their "god", and soon they simply had legends of false ones who claimed to be gods. They lost any reference to Marduk and forgot about their Stargate compeltely. Despite this, the true knowledge did continue on the planet through the "jaffs"; descendants of the priests who had once rebelled, who passed down the legacy in an oral tradition to their offspring. It was only these beings who knew what dangers awaited the people of Zigara when their Stargate was re-discovered in an archeological dig in the late 1900's. Despite the jaffs lobbying to have the gate reburied, they were able to convince the government to significantly expand the funds for research into the technology found at the dig; due to this, the Zigarans weapon technology had advanced much further than their other fields of technology by the time they started travelling through the Stargate.
Unfortunately for the Zigarans, one of the first worlds visited by them through addresses they discovered in the ruins of a building close to the Stargate was one controlled by the Goa'uld Bel. Bel managed to capture some of the Zigarans and, through interrogation, discovered how important their world could be to him. He sent a surprise attack to the Zigarans on their homeworld who managed to capture both the Stargate and the caves surrounding it. The forces of Bel continued to advance from this point but, when the Zigarans unleashed their new prototype weapons which had been reverse-engineered from Goa'uld devices, Bel's forces were held back. Thus, the two sides entered into a stalemate with neither side managing to gain advantage over the other; Bel was always limited to sending his troops through the Stargate and the Zigarans were cut off from any outside help from the Stargate. The Zigarans knew, however, that the Goa'uld would eventually either break their lines or deduce their stellar location and send a fleet of ships to attack from orbit. Because of this, they redoubled their efforts to crack the technology they managed to salvage from the ruins; they were eventually able to set up some ring transporters that gave them instant access to their moon base. This base was simply the prelude to a massive expansion they had planned which they hoped would turn their base into a bulwark of defenses against any attacks from deep space. (RPG: "Living Gods: Stargate System Lords")
Despite the defenses amassed by Bel to stop any Zigarans from escaping their planet, a lone army captain eventually managed to break through and dialed out to an address the jaffs recalled as being forbidden by their former false gods; the planet Cimmeria. He managed to make it through, though was wounded, and all the enemy Jaffa who followed him were taken by Thor's Hammer. Once the captain had been nursed back to health by the Cimmerians, he requested their help in defeating Bel's forces. The Cimmerians recognized this threat to be from the "ettins" and so placed the soldier in contact with Stargate Command. (RPG: "System Lord Plot Hooks")