Horsemanship is a keyword ability that makes your creature hard to block in combat. A creature with horsemanship can't be blocked except by other creatures with horsemanship. This ability has similarities to flying, but was only used in the Portal: Three Kingdoms set.
Horsemanship is a static ability and an evasion ability. A creature with horsemanship can't be blocked by creatures without horsemanship. A creature with horsemanship can block a creature with or without horsemanship.
- Creatures with horsemanship can still block creatures without horsemanship just fine
- . . .with itself: Multiple instance of horsemanship are redundant
- . . .with flying: Creatures with flying cannot block creatures with horsemanship. Similarly, creatures with horsemanship cannot block creatures with flying. While the abilities are similar, they are still distinct.