Maybe it's a little too early to say, but I don't feel good about this one.
It has to exhaust each time an offering is placed on it, and it needs to exhaust again to give an investigator an extra action. That's a minimum of 4 turns before it's given you back the action you spent playing it. And another 4 before it's provided actual benefit. You need to be consistently placing doom on cards for the first 3 of those 4 turns for it to be even that quick.
There is something to be said about holding onto the offerings for later, as a sort of budget borrowed time. But considering how contested the accessory slot is for mystics, it's a hard bargain.
Maybe this will be the cycle that adds support for uses (offerings). Considering the term, it would be interesting to see something that requires a sacrifice of some sort to get you some extra offerings on your cards.