Minecraft wiki entry for Gathering_resources_on_peaceful_difficulty, associated text: Gunpowder is not necessary for completing anything major, but it is fun and in many circumstances, helpful to use, as it can be used to create fireworks and TNT. Also, gunpowder can be used to make splash potions. However, no potion can be made on Peaceful, because brewing requires blaze powder as fuel, which are not achievable if blazes can't spawn.