A Defense potion is a potion that can be made with the herblaw skill. It requires level 30 herblaw to make and gives 75 experience. When consumed, the players defense level temporarily increases by 10% + 3. (rounded down)
To make a defense potion, first add Ranarr Weed to a vial of water creating an unfinished ranarr potion, then mix in White Berries. As with most potions, you initially make 3 doses of the potion and the doses decrease as you drink them.