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