On my current play through, I'm playing a stealthy thief/assassin, with the self imposed restrictions of not smithing/enchanting any gear or using any spells, only relying on bought/looted items and alchemy.

My plan was to be able to rely on potions/poisons for illusion school effects , such as invisibility and frenzy. In fact, I've been able to whip up some great poisons, that boosts a target's health, stamina, and frenzies them. Perfect for clearing a large group..or so I thought.

It seems that I am only able to mix poisons with a frenzy effect that works on creatures up to level 6...and I am level 20. What I don't know, is there any way to increase this restriction? Is it a function of:

• Alchemy Level - Will increasing my alchemy skill and wearing +Alchemy gear increase frenzy poison levels?
  
• Illusion Level - Would increasing illusion skill effect the "frenzy" component of a potion? (I'm willing to level illusion by repeatedly casting muffle on myself if need be)

Also, I would love it if someone could point me to an online resource that details poison recipes.

Thanks!

I am making frenzy potions that say they work on stuff up to level 14, and i only have alchemy leveled, no illusion. So i guess that kinda answers it. http://skyrim.melian.cc/?cmd=cmdSkyrimAlchemyWizard is a page i use for my alchemical endeavours, hope it helps. Although if you planned on using the illusionistic potions, i'd advise you to consider illusion instead, since it does not seem that poisons can reach the magnitude of spells. Oh and there's a list of some useful potions/poisons on uesp: http://www.uesp.net/wiki/Skyrim:Useful_Potions (use it, love it )

I was hoping to be able to use poisons instead of the illusion tree and avoid magic all together.

With Alchemy at 100 and with 5/5 of the Alchemist's perks I can make a Frenzy potion for up to level 12 (I'm level 81). This is improved as a Necromage Vampire (the level of enemy increases without it showing and increase in the tooltip), and would be improved by using the 'Poisoner' perk.

With Fortify Alchemy gear as a Necromage Vampire and perked out I can get a Frenzy potion that will work on enemies up to level 37.

Some great ingredients to get if you want to make poisons that are more powerful than 'average':
Crimson Nirnroot
Deathbell
River Betty (fish).

My favourite poison to apply to a bow for an 'instant' stealth kill:
Paralysis/Damage Health/Damage Stamina: Crimson Nirnroot+Canis Root+Imp Stool.