They are the bosses of planets (and Castle Greedy) in all versions of Ristar.
“Kaiser Greedy is the final boss of the game Ristar. Kaiser Greedy is a power hungry dictator...Kaiser Greedy
“Adahan is a boss in the game Ristar. Adahan is a small representitive of the Mole Civilization...Adahan
“Ohsat is a boss in the game Ristar. Ohsat is a purple and blue hammerhead (shark) who invaded...Ohsat
“The Armored Tree Snake is the mini-boss of Planet Flora in the game Ristar. Other than this...Armoured Tree Snake
“Riho is the first boss in the game Ristar. He appears in the opening, scaring some of the Flora...Riho