D20r:Druid

'''Entrench (Su):''' As a move action, you may create an entrenchment. A trench is 15' long, must begin and end in squares you are adjacent to, and must be in a straight line. A trench creates a 5' wide by 15' long depression into the ground, and on one side of it a similarly-sized pile of packed earth. An entrenchment created in this way is permanent, though it can only be formed from dirt, soil, or other loose ground. The depression dips down five feet, and the embankment similarly rises five feet--a creature with a reach or ranged weapon behind an embankment threatens as normal, but a creature within the trench does not threaten the other side of the embankment. Climbing up the embankment from within the trench requires a Climb check at a DC equal to 10 plus your druid level plus your Strength modifier; climbing up the embankment from outside the trench requires a Climb check at half that DC. Trenches are occasionally filled with water or other liquids: if so, they inflict movement penalties (and occasionally damage) as appropriate. Multiple applications of this ability (whether over a long period of time or by multiple druids working in unison) can create fortifications, moats, irrigation, or streams. This ability is usable once per encounter.