Climbing

While climbing, each foot of Movement costs 1 extra foot (2 extra feet in difficult terrain), unless a creature has a climbing speed listed. At the GM’s option, climbing a slippery vertical surface or one with few handholds requires a successful Strength (Athletics) or Dexterity (Acrobatics) ability check.

Climbing Speed

A creature that has a climbing speed can use all or part of its movement to move on vertical surfaces. The creature doesn't need to spend extra movement to climb.