Generally speaking:
- Your actions in the previous chapters decide what kind of relationship you have with Don, how much you trust him, etc.
- When you get into the last chapter, these decisions decide which endings are possible.
For Abeo Mors specifically, your Amanda clearly does not trust Don and doesn't want to listen to a word he says. (or your Amanda trusted him somewhat, but you decided to confront him about this and were not convinced by what he said).
If you Amanda fully doesn't trust Don when you reach the final chapter, you can only get one of three endings:
Note: Animus Liberatio requires the stranger to be alive, i.e. you did not tell Don about him.
Note 2: Both cases where you
, you need to do it at a very specific time. You need to
.
The other two endings are available if your Amanda trusts and/or loves Don when you reach the final chapter, or she semi-trusts him and you listen to him when he explains his version of events, and you choose to believe him.
There is "Sequence Selection" option in the game's menu where you can start the final chapter with different disposition toward Don, which will let you more easily experience all endings, if you're only interested in them and not the steps leading up to it through the previous chapters.