I found somewhere to exchange your amulets for the corresponding shards, but the shards seem to be hugely less valuable than the amulets. So can someone explain to me what amulets are used for and why they seem to be fairly valuable?

turning in amulets also has a chance (approximately 1 in 7-ish) to give you a tome, which can be used on a pet to boost their stats. this is especially valuable for higher-level pets, when training a single stat takes the better part of a day.

Ohh. That makes sense. I'm not huge into the battle scene, so I'll just stick with selling them. Thank you so much :)

The other consideration is that tomes sell for significantly more than amulets. If able to gain at least two per ten turned in (and there's decent odds of that), then you'll usually make a noteworthy amount more than if you had just sold the amulets separately. But it's a bit of a gamble, and if you only get a few amulets a day from Quentin (as is usually the case) it doesn't feel very good to get nothing a few days in a row and then a bigger payoff. Something to consider, depending on if you prefer a slightly smaller but more consistent income, or if you are at all a risk-reward person (which makes this sound like a bigger risk than it is LOL it's generally going to average out to more.)