Main Endings - Once you collect the three crystals from the forest, snow mountain and volcano, you can return to the town and either empower the seal, if you have allied with the empyrean who speaks to you outside of town, or simply give them to Ptolemy. 

Side Main Endings - If you side with the empyrean and empower the town's seal you can choose to speak with Ptolemy and battle him.

Bad Endings - Most enemies within the continent attempt to corrupt Derrick, if said corruption reaches 100 then you will get an ending.

Special Ending - There are various special events which trigger within the Orc Fortress and southern passage cave. You know will get a trigger for them by scavenging.