I need a creative and IRL way to show the progress of a cult to my players

I'm running a campaign set in a massive metropolis, and aside from the secondary conflicts, there's an "evil cult" performing a major ritual.

Each day, the cult gains “2 successes,” and after reaching 10 successes, the ritual is completed. There are some things the party can do to reduce the cult’s successes or even stop the ritual altogether.

I've used this mechanic several times before, but this time the PCs are going to find a magical device from a cultist that lets them track the ritual's progress.

That’s where I need help.

I need a cool and fun (and dark) way to represent this magical device, but I don’t know what to do.

I can make something DIY. Do you have any ideas?

(The impacts in game of the cult actions, depending of the progress of the ritual)