Difficult Terrain halves the Movement Speed of creatures moving through it; that is, a creature must spend 2 m / 6 ft of movement to move 1 m / 3 ft through an area of difficult terrain.
Examples of difficult terrain include:
- Web, mud, vines, lava, deep water, grease, ice, spikes, and many other types of Surfaces.
- Non-surface areas created by spells such as Hunger of Hadar.
- The overgrowth created by Plant Growth uniquely quarters movement speed.
The extra expenditure for movement also applies to Jumping. Furthermore, Weapon actions that require expending movement will not function while the character is effected by Difficult Terrain. These include Brace (Ranged), Brace (Melee), and Prepare.