This idea is for basically a supercharged Totem of Undying. It functions the same as a totem of undying(if you are holding it you don't die), and has the same texture except enchanted. The 'lore' of the item says something along the lines of 'Charges: #' or 'Lives Left: #'. You charge the Relic by crafting it with a Totem of undying, and each time you 'die' it loses a charge and keeps you alive. Its a compacted Totem of Undying. It can have up to 3 charges. The Relic is obtained from the coin shop for 16 wildercoins, because you have to recharge it yourself. If you think that just crafting a Totem with it is too easy, you could have it gain 'charges' by killing an Evoker while holding it(so you need to kill it instead of just getting the drop, so you can't just 'buy' charges.

This is certainly an interesting idea. That's a good way to compact totems of the undying into a single item. However, a type of recharge mechanic might be a bit tough to balance around. By being able to recharge it, you can potentially never die, which might go against the survival spirit. I'm sure a fair balancing mechanic can be made for it somehow though.

To be fair, you can always just carry 3 relics with you... or a shulkers worth... or an enderchest that has shulkers worth...

There's a lot of ways you can basically do this vanilla to avoid the risk of dying, the better question is if there's a market for this type of item. I don't see it as a balance issue anymore than shulker boxes are a balance issue. I'd be curious if there should be a downside (perhaps you can have 3 charges, but you have -2 health [-1 heart]), so you're more likely to need it while it's in use.

maybe if it's in your offhand you get a very mild Hunger effect?