A creature with both flying and shadow has two separate evasion abilities, and a potential blocker must satisfy the restrictions imposed by each of them independently. Reach only addresses the flying restriction; it does nothing about shadow.
Shadow (CR 702.28) states that a creature with shadow can only be blocked by creatures that also have shadow, and it can only block creatures with shadow. This is a blanket blocking restriction entirely separate from flying.
Reach (CR 702.17) states that a creature with reach can block creatures with flying, effectively treating itself as though it could block 'in the air.' However, reach grants no special interaction with shadow whatsoever.
Because both restrictions must be satisfied simultaneously (CR 509.1b requires that no blocking restriction is violated), a creature would need both reach (or flying) and shadow to legally block a creature that has flying and shadow.
Example: Your opponent attacks with a 2/2 that has both flying and shadow. You control a Spider with reach. The Spider cannot block it — reach handles the flying part, but because the Spider lacks shadow, the shadow restriction still prevents the block entirely.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.