Player's Handbook[]
A character with this proficiency can make difficult and dangerous climbs up steep slopes and cliffs with the aid of spikes, ropes, etc. If a character with mountaineering proficiency leads a party, placing the pitons (spikes) and guiding the others, all in the party can gain the benefit of his knowledge. A mountaineer can guide a party up a cliff face it could not otherwise climb. A character with this proficiency gains a 10% bonus per proficiency slot spent to his chance to climb any surface. Note that mountaineering is not the same as the thief's climbing ability, since the latter does not require aids of any sort.
Player's Option: Skills & Powers[]
Mountaineering: A character with this proficiency is skilled in the use of hammer and pitons (spikes) to secure a route up a mountainside. He also knows how to use the rope and brackets that can link a party of climbers. A proficient character can make a route across a steep section of rocks, and by the use of ropes allow other, non-proficient characters to follow.
No proficiency check is required unless the DM declares that a route is very perilous- steeply pitched, with few hand- and foot-holds, and those that exist are tiny or loose. If a character connected to the mountaineer by rope falls, the mountaineering character can make a proficiency check; success means that the otherís fall has been arrested. Failure means that the other character continues to fall, and failure by a roll of 20 means that the mountaineer is pulled down, too.
Characters with the mountaineering proficiency can add their proficiency rating to their percentage chance of climbing any surface; this includes thieves using the climb walls special ability.