Like skills, equipped potions should have a feature to unlock their leveling in 167-189 expeditions. So they would give passive attributes - always enabled.

Example when the potion is equipped it grants (the range is based on lower to higher potions grade/level):

Ultimate Health Potion:

+1~20% hp
+1~20% force shield
+1~20% HP regen

Ultimate Willpower Potion:

+1~50% spell damage
+1~50% elemental damage
+1~50% willpower regen rate

etc....