Tunneling

A creature with a tunneling speed can tunnel through sand, loose soil, or gravel, but treats areas of solid rock as difficult terrain. This movement works only through natural, undisturbed materials, and cannot be used to move through manufactured or constructed structures, such as walls, foundations, doors, portcullises, shutters, or any other 'made' thing. Using tunneling requires only as much concentration as walking, so the creature can attack or cast spells normally. The path a tunneling creature takes through the earth does not collapse behind it, but instead leaves a stable cave of a diameter equal to the tunneling creature's girth. Tunneling does not give the creature the ability to breathe underground, so when passing through loose material, the creature must hold its breath and take only short trips, or else it may suffocate.

A creature with tunneling must be able to trace line of effect to any creature it wishes to attack. Since line of effect is always bi-directional, a creature cannot use tunneling to make attacks while being immune to attacks itself.

Attacks of opportunity against creatures with tunneling rely on the attacking creature's ability to draw line of effect to the square the tunneling creature just left. That is, if the tunneling creature is on the surface, and tunnels into the ground, leaving a threatened square, the attacker probably has line of effect and can therefore make an attack of opportunity. However, passing under a creature while tunneling probably does not provoke attacks of opportunity, as the would-be attacker probably can't draw line of effect into the ground (unless he also has a tunneling speed, for example).

Creatures with tunneling usually gain a +2 training bonus on Might checks, to emulate their often strong, sturdy nature (even though checks to determine the success of tunneling are always made with the Movement skill).

• Prone: A creature with a tunneling speed cannot be made Prone, but any time they are subject to the Prone condition, they are instead Immobilized until they expend a move action to reorient themselves. Spending a move action to clear the Immobilized condition does not provoke attacks of opportunity.

• Difficult Terrain: Tunneling generally allows a creature to bypass difficult terrain, since they can just go under or around it, even when passing through the ground surface which is deemed difficult terrain (unless it is made of stone).

• Permitted Movement: The tunneling creature cannot charge, make 5-foot steps, run or withdraw.

• Overland Travel: Outside of combat, tunneling creatures travel overland at the same pace as a walking creature of the same speed.