Unless stated otherwise, magical potions grant the drinker a given magical ability for 1d6+6 turns. And get rid of those generic potion bottles by using the Random Potion Container tables.
Mage Blood, Lesser
This potion is made from the blood of a magic user of level 4 or lower. It is not consumed, but is smashed on the floor while casting a spell. The target of the spell makes any saves against the effects of the spell with a -1 penalty.
Mage Blood, Greater
This version of the Mage Blood potion (above) is much rarer, requiring the blood of a magic user of at least fifth level. It is treated as its lesser cousin, but produces a -2 penalty.
Poseidon’s Wine
The user gains the benefits of the water breathing spell. This wine is usually found in a larger bottle than most potions, containing 6 ‘doses’ of the potion.
Saddle Born’s Draught
The user gains the benefits of the Horseman’s Potion (+1 on all attack rolls and saving throws while mounted, and his mount gains these same bonuses), and also gains the ability to speak with horses, hippogriffs, griffons and pegasi.
Satiety
This potion eliminates the need for food or drink for 1d6 days. The user feels neither hunger nor thirst but can still eat or drink if he pleases. At the end of the duration, there are no ill effects from having not eaten or drunk for the duration.
Shadows
After imbibing this potion, the user casts no shadow. Instead a shadow replaces his natural shadow and follows his orders, even to the death. It can travel up to 240 feet away from the user in pursuit of its orders.
Love the Shadows potion! The effect would be a great special ability for some kind of dark class or race.
All the potions are cool, and I agree with Peppe: Shadows takes the cake.
I’d be very tempted to rule that, if the shadow is killed while under the user’s command, the user loses his shadow. This might give some bonus to stealth-based skills in certain circumstances, but seems like it should have penalties perhaps to social skills, because “something seems unnatural,” or simply something like unbearable nightmares.
Regaining one’s shadow could be an incredible character-building journey. I can also imagine a hardcore thieves’ guild whose members are required to intentionally sacrifice their shadow.
The shadow thing reminds me of a specific spell in the Belgeriad books–mages could send their shadows long distances away (they didn’t look like shadows, but like clones of the originals, minus a shadow, of course). Then, one time, the magess blasted a group of shadowing-mages, and destroyed their shadows forever.