Effect and affect are both verbs. They are also both nouns.
effect n. meaning as you described: "The effect of the potion was that I grew three sizes."
affect v. meaning as you described: "The potion affected everyone the same way."
effect v. meaning "to successfully cause": "The potion I'm mixing will effect a revolution among the goblins."
affect n. meaning face or appearance: "Realizing she was about to drink the life-changing potion, the goblin's entire affect shifted to delight."