Hi! Glad you're liking the game.
Jolly Co-operation: A friendly NPC summoned this way is Level 1 and has a random Class, as a way of succinctly giving the player some stats to work with (3 HP and MP, 2 Strength, a random Power and HP/MP boost). I didn't intend to give friendly NPCs Sunlight Drink or other Items, but the rules are ambiguous, nothing says they can't have or use Items, and it would be a little inconsistent to use only some of the Hollow's character setup list. Short answer, NPCs can have starting Items like the player character would. Just keep in mind that they can't gain more Items during play ("you" refers only to the player character when the rules mention gaining Items and Souls), and they are limited by the same rules as the Hollow when using Items and Powers. On that note, a character may use Items or Powers up to [their level] times, but not Items and Powers in the same turn. The Hollow and their NPC allies use Items and Powers separately (you are not using their Power, they are), but since they are Level 1, they can only use a Power (or an Item) once per round.
Each round of combat, dice pools are rolled for each side of the combat, so if you have an NPC helping you, roll the group's dice together and pair them off against the enemy side's dice as you like. (Or, simply deal damage based on dice showing 4+ if using the Furtive Grasp rules.)
The first rule in resolving dice pairs says that the lower die's owner takes damage; if you want to be technical about it, you might roll the Hollow and the NPC separately (or with different-colored dice), keep track of how they all pair against the enemy, then deal damage accordingly. But personally, I would just distribute the damage between allied characters as you like. (And in case of Furtive Grasp rules, you kinda have to do this, since the enemies don't roll dice.)
Randomizing Realm Creation: your idea sounds pretty cool! For Embers of Morndrin, I stayed fairly minimalist about building out the world mechanically, but it's definitely open to experimentation and add-ons. If you do try out your idea, please let me know how it goes!
































