Ok, here's the plan. My players are 7th level. They have inadvertently led the bad guys (a wannabe lich and crew) to the location of an artifact they were sworn to keep secret. Since the hiding place is blown, they will be charged with protecting the artifact and fleeing. The artifact is one of the bloodstones of Arazni. Once they are in possession of the stone, they with gain a mythic tier.
After that, they will eventually figure out what it is by researching in Absalom or maybe last wall (they are currently in Ustalav). Then they will be encouraged to find the remaining bloodstones and then confront Arazni with the combined power of the bloodstones to defeat her. Each bloodstone will be a major quest that will take them multiple levels to complete. They will be hounded every step of the way by Arazni's grave knights, and possibly some crazy Iomedae/Aroden worshippers.
I want to tie adding mythic tiers to accumulating more of the stones. So I'm going to skip the lesser trial rules, and give them more tiers when they get their hands on each stone. I am wondering how to spread out the tiers. Should I give them 2 tiers per stone (so all four would put them at 8) and the last two if they defeat Arazni? Or just stick with 1 per stone?
Thoughts? It all seems a bit Monty Hall, but I can surely keep them challenged ;). Also, the stones have a serious drawback.