It's not a shield, but it acts like one. It's a little ring for when you can prick yourself at will, allowing you to cancel any animation but at the cost of a pip.

If you carry a key, vial, totem, or statue, you can immediately drop it.

If you shield bash or dash, you can cancel it.

If you cancel a charge attack. Well. You lose more pips because those are hard to cancel. Except bombs.

You can also cancel your pet skill, but the cooldown is still there.

Ancient gear becomes a significantly different experience. Well, every loadout really. But Ancient even more so!

With really precise timing, you can be invincible through attacks.