The Nintendo DS title "Glory of Heracles" is a turn based RPG.
Orthros is a boss character in a mine. The tricky thing about defeating him seems to be that when you think you've got him beat, he doubles or triples. I've killed him seventeen times, or more, but each time I do a final attack that has enough HP damage to finally kill him, he survives it, and replicates. I'm randomly experimenting with the magic I have available, and physical attacks ,and it seems that the "elemental ether scores" at the top of the screen are the key to the puzzle, and if one can find attacks that show an up-arrow icon then they are 'more effective'... The party has three characters, level 9 at the beginning of the battle, in my case. This may also be part of the problem. Perhaps you need to grind longer and arrive at this quest with level 10 and more magic?