Potions are herbal infusions that can be made using Herblaw skill. An odd potion called 'Potion', however, can only be gotten from Imp or Apothecary in Varrock. Potions have a wide variety of different effects depending on the ingredients used. Most potions are consumed orally but Weapon poison can only be applied to certain weapons.
Basic formula for making a potion is the following: vial of water + Herb + Secondary ingredient = Potion
Herblaw-made potions contain 3-doses and each drinking takes one dose off. Some monsters drop one- or two-dose potions and the Apothecary can make four-dose Strength Potions. There is no way to decant potions in Runescape Classic.
Once the potion is fully consumed the player will be left with an empty vial.