Sadola is a mollusk-like kaiju that has appeared several times in the Ultraman franchise, making its first appearance in episode 3 of Return of Ultraman.
Return of Ultraman
Sadola was first spotted by Hideki Goh, though no one at MAT believed him when he told them of it. Sadola later attacked the captain, prompting Goh to investigate. Goh later found the captain, but they were both ambushed by Detton. Sadola then appeared to fight Detton, prompting Goh to transform into Ultraman Jack. Jack killed Detton with the Specium Beam, while destroying Sadola with the Ultra Slash.
Multiple Sadolas appear in Ultraman Mebius. One was eaten by Bogar, while another fought against Ultraman Mebius. After Mebius defeated the kaiju, two more appeared and attacked him, but both wound up destroyed by Ultraman Hikari.
Ultra Galaxy Mega Monster Battle
Multiple Sadolas again appear in this series.
Five more Sadolas tried to attack ZAP SPACY, but all of them were destroyed by ZAP SPACY's missiles.
Mega Monster Battle: Ultra Galaxy Legends The Movie
Sadola appears as a member of Ultraman Belial's 100 Monster Army. He was killed by Ultraman Zero's Zero Sluggers.