alignment merits
They don't drop. They are earned by 'reaffirming' yourself as a hero/villain. If you are a hero, and do hero tip missions, eventually you'll get a hero morality mission. The first time you get 50 normal merits; ever after you'll get one hero merit. Same goes for villains.
You can also buy one every day in the crucible/fort trident for 20 million+50 merits.
Note: changing grey or to the other side deletes purple merits.
Thank ya very much, the info I had read was a bit vague and I've yet to reaffirm any alignments. I knew about the 50 reward merits after reaffirming but I was wondering how many AM's you'd recieve after that. Appreciate it!
Also worth noting, reward merits do NOT scale with mission difficulty. If an arc gives 10 merits, it gives 10 merits whether your difficulty is at -1 or +4.
Paragon City Search And Rescue
The Mentor Project
I suspect that the OP was referring to the inherent difficulty of the mission, ie one that is more difficult, and therefore takes longer, not the difficulty settings. But your note is probably worth adding for the benefit of others who stumble in here.
@Roderick
So, what's the drop rate like for alignment merits? Is it scaled like reward merits due to mish difficulty?