Cobalt Shield

The defense is a rounding error. The reason to wear this is that nothing shoves you anymore. Being knocked backward is how most early deaths actually happen: a bat clips you over a lava pool, a demon eye bumps you off a rope, one hit during a boss run puts you in the wall behind you. Removing that turns a lot of unsurvivable chip damage into survivable chip damage.

It is also the entry point for a long upgrade chain. Everything worth wearing later that keeps you immune to knockback traces back to this shield, so pulling one out of a Dungeon chest early saves a return trip. Hold onto it after it leaves your accessory bar.

Much later it pairs with the Brand of the Inferno if you want a real block. Holding a shield up is only worth doing when a hit cannot stagger you out of the stance.

It has nothing to do with cobalt ore and has never needed a single bar of it.