The questions we are asking are:
"How are the story/experiences being imprinted on the Crystal"?
and
"How are the story/experiences being read/experienced?
The "technical" aspects of how the Crystal works is integral to how you design the film both visually and sonically.
To posit a scenario - The Crystal is worn like a necklace and is enchanted to imprint the story/experiences of the wearers death, sort of a mind print. In this interpretation what is imprinted on the Crystal allows for the "viewer" to know what the protagonist knows, what is a reasonable "guesstimate" of the situation by the protagonist on what is partially known, and what the protagonist only wild-ass-guesses/surmises, (which are usually integral with characters fears) and the difference between the three. All the experiences are as the protagonist perceives them. It is primarily POV, but still allows for visualizing the guesses and guesstimates (different shooting styles?). It can move back and forth in time and can even have seemingly "irrelevant" flashback sequences. When the Crystal is held by someone the holder experiences what is imprinted on the Crystal as perceived by the decedent. Anyone who holds the Crystal can participate in the imprinted experiences. The sound design style is wide open - from interpretive/minimal to hyper-real to over the top (the memories are, after all, colored by the protagonists/wearers perceptions) or a combination of all three. Production sound should be standard boomed mic and lavs.
Second scenario - The Crystal is carried around (in a pocket(????), records what is going on as if it were a camcorder and the story is told sequentially from the Crystals POV. This affects how it will be shot. It somewhat opens up if there is a reason for Crystal is pointed at what you want the audience to see; perhaps the Crystal "lights the way" either literally or figuratively or both (maybe it's a "map" of some kind?) - it's enchanted, right? It's still a very linear camcorder style, however. When the Crystal is held (or put into a "projector" of some kind?) the "viewer" sees what the Crystal saw. This puts a discrete set of boundaries on what and how you shoot. The Crystal is not going to be used like a microphone, so you need to think through the recording of the dialog and how the dialog is presented in the mix. Production sound again should be standard boomed mic and lavs, but, as I said, you have to think it through; do you POV the boomed mic or do you follow as much as possible and "dirty up" the boom and/or the lavs during rerecording. Your overall sound design will have to be carefully crafted as well.
These are just two possible scenarios, there are dozens more. How the Crystal works is important to how your film will be shot and the approach to the sound design which affects how you approach the production sound. We want to know the details of your scenario so we can discuss different approaches to shooting and sound-for-picture.
We're all locked up in our homes and have the time to talk film making. Lay out your project and lets all pick it apart. We've got the time to share our experience and knowledge, so take advantage of it. You don't have to take our advice, but you at least get the opportunity to see how we think a project through.