Righy ho.
I've always been a fan of the reader being able to decide the outcome of an event (or, the entire story.). So, when I started writing this story I always planned to have a little bit of multiple choice and let the reader decide what they want.
Time for you to chose what you want.

So... Ajax had two options.
"Would Ajax sacrifice himself in return for the guarantee that Equestria will be saved?

Will Ajax take a risk and try to repay Celestia by truly saving her from all of their enemies?"

If you want to read the first option, you'll want to read "The last enemy that shall be destroyed".
If you want to read the second option, you'll want to read "Back in black".
Or, if you want, read both! All down to you!