What is the Caraxes Chest for?

The Caraxes Chest is an event chest: it specifically boosts Caraxes and Zivern Relics. Opening it gives you a far better chance of growing those two particular dragons.

The appeal: if you play (or want to play) Caraxes or Zivern, it's the ideal moment to raise their Star Rank fast, since the chest concentrates their Relics.

Conversely, if those dragons aren't in your plans, the event matters less — better to save your keys and gold for a chest aimed at your key dragons.

It's the perfect illustration of how event chests work: they target specific dragons, so open them when the target matches your strategy.