Each time they attempt to cast a spell, after the casting dice have been rolled a Night Goblin Shaman must eat a Magic Mushroom. This adds 1D6 to the casting result. This dice does not count as a power dice, and cannot contribute to Irresistible Force. However, if you roll a 1 on this dice you must roll a further D6. On a roll of 4+ nothing else happens, but on a roll of 1-3 the mushroom was poisonous, and the Shaman suffers a wound with no armour saves allowed. Finally, unless it was cast with Irresistible Force, the spell automatically fails.