Cling
Version 0.16: This article may not be up to date for the latest stable release of Crawl.
Certain creatures can cling to the walls of the dungeon, allowing them to pass over otherwise impassable terrain as long as they stay orthogonally adjacent to a wall (they cannot cling to only a corner). Creatures that can cling to walls include (but are not limited to):
History
Prior to 0.15, players could cling using Spider Form or boots of the spider.