Requires Training: Yes.
The character with high tumbling is able to roll away from attacks during combat, positioning themselves safely at all times. Any time the character might receive an attack of opportunity for moving past enemies, they will automatically attempt a tumble check against a DC of 15. If successful the attack is avoided. For every ten ranks in this skill (not including Dexterity bonus) the character's armor class is also improved by +1.
Check: DC 15 to avoid attack of opportunity while moving.