Underfoot

You use your size against larger foes, quickly moving around them to avoid notice or stay out of reach. As long as you're Small, you can end a successful Tumble Through action in a Medium or larger enemy's space. The enemy must have appropriate limbs or otherwise leave you enough room for this maneuver, as determined by the GM. You couldn't, for example, occupy the space of an ooze that matches the full dimensions of the square. While you occupy an enemy's space, that enemy is off-guard to you. Underfoot leads to... Skulking Strike