Eisenblut (Haemocraft)

You infuse and harden the blood within your veins to such an extreme that it forms a protective armour just below the skin, guarding you from grievous harm. For the duration, your base AC becomes 15 + your Dexterity modifier, at the expense of your speed being reduced by 10, and Dexterity saving throws being made at disadvantage.

At Higher Levels. When cast using a spell slot of 5th level or higher, the duration is doubled and base AC increases by 1.