B/X House Rules: Potion Miscibility

 In working on the layout for Fang, Faith, and Legerdemain, I realized I had waaaaay too much room for illustrations in the Alchemy section. So I asked myself, "What additional content could I maybe put in that section?" 

Being a fan of Chris Stogdill's d30 Potion Miscibility Table (I've used it often in my games),  I decided a Potion Miscibility Table was the perfect addition. Also, I had completely forgotten the 1e DMG included one. 

I like the 3d6 roll vs. the d% used in the DMG because it's more B/X to me. Also, in this table, the chance of the "Poison" result on 3d6 is 1 in 216 (vs. the 1 in 100 chance from the DMG). The same is true of the "Discovery" result.

Anyhoo, here's my B/X adaptation of the Potion Miscibility rules. 

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Potion Miscibility

The composition of a potion is a complicated thing. The alchemist can spend weeks preparing the ingredients just so, then combining them in perfect balance. The composition of one potion is not always compatible with another. The miscibility of potions should be tested when either of the following occurs: 

1. the commingling of two (or more) potions
2. a creature still under the effect of one potion consumes another

It is suggested that, under such circumstances, a 3d6 roll be made on the Potion Miscibility Table (or a similar table of the DM’s own design) to determine the outcome of the commingling: 

Additional Considerations

The following considerations should be taken into account when using the Potion Miscibility Table.

• Contradictory potions (e.g., a potion of growth and a potion of diminution) will normally cancel each other out, but may cause additional miscibility effects. 
• A potion of delusion may be commingled with any other single potion without the effects of either being affected.
• Combining oil of slipperiness and oil of etherealness has a 50% chance of causing the imbiber to lost in the Ethereal Plane for 5d6 days.
• If three or more potions are combined, subsequent rolls should be affected by a negative modifier. (The modifier is at the discretion of the DM, and should be based on the similarity/dissimilarity of the potions’ effects.)