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Flying is the ability to move in air.

Flying Rules[]

Fly Speed
To fly, a creature may use a walk, run or charge action, but uses its fly speed in place of walking speed. A creature with a fly speed can also shift and take other move actions as appropriate while flying.
Moving Up and Down
A flying creature may move straight up, straight down, or diagonally up or down. There is no additional cost for vertical movement.
Falling prone
A creature knocked prone while flying will fall. They first safely descent a distance equal to their fly speed, but further squares can cause falling damage. The creature isn't actually prone until it lands and takes falling damage.
Remaining in the Air
A creature needs no special action to remain flying. However, a creature that is stunned will fall instantly.
If a creature flies to a surface it can hold onto or rest on, the creature can land safely.
Terrain on the ground has no effect on flying creatures. They ignore difficult terrain or other ground based hazards, but are still affected by aerial terrain.

Flying Traits[]

Altitude Limit
If a creature has a specified altitude limit, the creature falls at the end of its turn if it is flying higher than that limit (safely descending its fly speed first). For example, a creature that has an altitude limit of 2 falls at the end of its turn if it is flying higher than 2 squares (with ground level being considered 0).
A creature that can hover will remain in the air while stunned. It may still fall when knocked prone.