Shield
From SpiralKnights
Shields have defense and health, just like a player. When a shield blocks, any damage that gets past its defense degrades its health, which regenerates over time. Once a shield reaches 0 health it breaks. So even if the shield has no defense against a certain damage type, it still has a wall of health that can absorb the damage. Obviously if the shield does have the right defense less damage gets through, taking more hits before breaking.
This is a partial catalog of the shields that can be found on Cradle, sorted by rarity. The listed statistics are for a level 1 version of the shield.