Shadow

Shadow is a keyword ability on creatures that serves as both an evasion ability and a blocking restriction. An attacking creature with shadow can only be blocked by a defending creature with shadow, and a defending creature with shadow can only block an attacking creature with shadow.

From the Comprehensive Rules:

• 502.8. Shadow

• 502.8a Shadow is an evasion ability.

• 502.8b A creature with shadow can’t be blocked by creatures without shadow, and a creature without shadow can’t be blocked by creatures with shadow. (See rule 309, “Declare Blockers Step.”)

• 502.8c Multiple instances of shadow on the same creature are redundant.