They all have a certain importance in the story and everyone has their own features and personality. The fights with them can't be avoided and their defeat is fundamental to progress in the games. They usually fight alone with the exception of Rainheart and Parano, that summon standard enemies before or during their boss battles.
With the only exception of Clinic Chief Lem, they can't be killed by shorting. Compared to regular enemies, they have more health and different patterns of attack, making them much more serious of a threat.
In first game, they drop nothing upon being defeated. In the sequel, Rion will instead get a Skip as a reward.
If Rion is defeated by one of them in Galerians, the player has the possibility to Retry, facing the boss again. In Galerians: Ash, the Retry feature has been completely removed.