Axiomatic Aegis

You invoke the unshakable logic of prime numbers, wrapping the target in a shield of mathematical purity. Until the spell ends, the target's Armor Class is determined not by conventional means, but by the nature of prime numbers. While the spell is active, you gain the following bonuses:

• All attacks against the target ignore attack bonuses.
• Only prime numbers on an attack roll (2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31) hit the target.
• Any other number automatically misses, regardless of attack bonuses.
• Because 20 is not a prime number, the target cannot be critically hit.