The Thiima, also known as the Shiima (シーマ) are the antagonistic race in G-Darius and make their first appearance in that game.
The Thiima (which means "Deliverer of Death") were a race of mechanical life-forms covered in a hard metallic material. Their flexibility, speed and destructive power made them almost indestructible. They lived to protect the peace in the universe and so they attacked Amnelia in Amnelian year 626 after the appearance of the A.N.. They were ultimately defeated by Sameluck Raida and Lutia Feen in the same year. Later, Belser acquired and utilized Thiima technology in their own battleships.
They also appear in the Dark Helios/Syvalion ending for both Dariusburst and the iOS enhanced port Dariusburst: Second Prologue via the appearance of The Embryon. In the case of the original game, we learn in the ending that Ti2 has a framework based upon the Thiima and thus it gives her a common link with them.