From DDO wiki
An alchemical bonus is granted by the use of a nonmagical, alchemical substance.
Sources of alchemical bonus in DDO:
- Spell Power potions and clickies, such as Ardor can increase the power of your spells
- Alchemical Weapons (Tier II Martial effect) grant a +2 bonus to an ability score
- Tenser's Transformation spell grants a +4 bonus to Strength, Dexterity, and Constitution
- Alchemical potions, such as Potion of Influence or Potion of Bull's Skill provide bonuses to ability scores or skill checks
- Eldritch Rituals to Armor and Shield (See Stone of Change recipes)