A secret scouting mission to the Massassi Site on Yavin 4 was performed at the behest of Palpatine, Supreme Chancellor the Galactic Republic, a little over four months after the onslaught of the Clone Wars. The Chancellor, who was in fact the public persona of a Dark Lord of the Sith called Darth Sidious, knew that Yavin 4 had once belonged to the ancient Sith Empire. For that reason, he wanted to ascertain whether any worthy Sith artifacts could be recovered from the Massassi Site. Mas Amedda, Vice Chancellor of the Republic, was dispatched in secret on Yavin 4 with an escort of elite clone troopers. He returned to his master with samples of carnivrorous piranha beetles, which pleased Palpatine.
In 22 BBY, the Galactic Republic went to war with the Confederacy of Independent Systems in a devastating conflict known as the Clone Wars. Unbeknownst to most of the galactic community, both sides were led by the same man, a Dark Lord of the Sith who was known to the Republic as Supreme Chancellor Palpatine, and to the Confederacy as Darth Sidious. He masterminded the whole conflict in an effort to bring the galaxy under Sith rule with him as ruler. Four months after the onslaught of the war, a fierce duel occurred on the moon Yavin 4 between Anakin Skywalker, a rising star of the Republic-aligned Jedi Order, and Asajj Ventress, a commander of the Confederacy.
Shortly after the duel on Yavin 4, which resulted in the apparent demise of Ventress, Palpatine took an interest in the many ruins present on that moon. Knowing of Yavin 4's past affiliation with the Sith Empire of old, and he wished to recover any worthy dark side relics from the ruins. To this end, Palpatine secretely dispatched his vice chancellor Mas Amedda to scout the ruins, with the protection of several elite clone troopers. While Amedda could not find any artifacts, he did not return empty-handed. The Vice-Chair managed to bring several piranha beetles, a species of carnivorous insects. Palpatine was satisfied with that discovery, and he immediately foresaw how he could use those insects in the future.
Many years later, Palpatine, now sole leader of a Galactic Empire, found some use for the killer insects that Amedda had once introduced to him. When the Death Star, the Empire's planet-killing superweapon, was destroyed by the enemy Rebel Alliance, Palpatine elected to have Bevel Lemelisk, one of the chief designers of the superweapon, torn apart by a swarm of angry piranha beetles.