Here's how it is!
Then = a shift in time
Than = a comparison of two things
Examples:
He wrote, then he edited, then he published. (Synchronous order of three verbs)
She screamed rather than speaking softly since she was an eagle. (Comparison in audible volume)
The devil ate their souls whole, then felt remorse since he would rather have burned them.
He did this then that.
He did this rather than that.
No one knew the answer better than him.
The synchronous rhythms hummed softly then slowed.