Galden is the main antagonist for the majority of the show.
Near the middle/end of the show he cuts his ties with Idoro, and continues fighting on his own.
Then in episode 44 he falls under the control of a hell dragon woman, though in the end he overcomes her spell and gets injured fighting for, or with the other Ryus and nearly dies.
After this most of the Ryu riders accept that he might be a good guy after all, all except Sarutobi. Who cannot forgive Galden for stealing his spirit stone.
But in the next fight Galden returns the stone to Sarutobi, gaining Sarutobi's trust only after he appears to die. As it turns out he did not die but was saved by the white dragon and comes to help fight in the last big battle of the series.
After which he says that he is going to try going to the country in which he was born. Then decide what to do after that.
The last time we see Galden he is walking away with his back to the group and waving.