Does a Weapon Siphon with Bottled Sunlight deal both Fire AND Vitality damage?

Question

Weapon Siphon adds 1d4 of an alchemical bomb's damage type to a weapon, but what happens when the bomb deals two damage types?

The bomb must be one that deals energy damage, such as an acid flask, alchemist's fire, bottled lightning, frost vial, or thunderstone. The next three attacks made with the weapon deal 1d4 damage of the bomb's damage type in addition to the weapon's normal damage.

-Weapon Siphon

The bomb deals 1d4 positive damage and 1 positive splash damage, as well as 1d4 additional fire damage

-Bottled Sunlight

Both Fire and Positive (now called "Vitality") are energy types, making Bottled Sunlight a valid option to use with the Weapon Siphon.

Does the weapon siphon add 1d4 fire damage, 1d4 vitality damage, or both?

Answer 1

Probably not

This is a tricky one, and could definitely go either way at a given table. However, I believe the by-the-book answer is that it will only deal positive damage. I only have a couple reasons to think so:

• the fire damage is described as 'additional', implying that it is not the damage of the bomb (kind of)
• it's ambiguous and 'too good' to be true*

Ambiguous Rules
Sometimes a rule could be interpreted multiple ways. If one version is too good to be true, it probably is. If a rule seems to have wording with problematic repercussions or doesn't work as intended, work with your group to find a good solution, rather than just playing with the rule as printed.

*It's not 'too good' in the sense that it would break the game, but it is much better than the other options which do half the damage. I would personally allow it to do both damage types for the investment into the weapon Adjustment partially because of the limitation that would only affect undead (with the proviso that it is not a general ruling and would potentially require revisiting for other bombs).