Hah! Impossible to get four effects? Try making
Five-effect potions!
Jarrin Root + Human Heart + Blisterwort is a five-effect poison. (Damage Health, Damage Magicka, Damage Magicka Regen, Damage Stamina, Frenzy)
You can also make mixed-bag potions:
Creep Cluster + Mora Tapinella + Scaly Pholiota is a five-effect potion with a grab-bag of four positive effects (Fortify Illusion, Fortify Carry Weight, Regenerate Stamina, Restore Magicka) and one negative effect (Weakness to Magic).
Glow Dust + Glowing Mushroom + Hanging Moss is a five-effect potion with three beneficial (Fortify Destruction, Fortify Health, Resist Shock) and two negative effects (Damage Magicka and Damage Magicka Regen)
Bear Claws + Hanging Moss + Sabrecat Eye is another five-effect potion with the same two negative effects as the above, and Fortify Health, Fortify One-handed, and Restore Stamina as the positive effects.
Silverside Perch + Daedra Heart + Sabrecat Eye is a fourth Five-effect potion that doesn't know what it's trying to do: Damage Magicka, Damage Stamina Regen, Restore Stamina, Ravage Health, Restore Health. I guess it's useful in a pinch, but it takes back everything it gives you
