Hey folks,
I'm a long time DM and follow the forums closely, but this is the first time I've felt the need to reach out with a question of my own. My current campaign has been running for almost two years, and I've given the players a lot of options in changing mechanics or creating new effects; I like to be a 'sure, give it a try' rather than a 'no' DM.
I've worked with my players on several homebrew effects that seem to be balanced and work well in the campaign, but these have been things like trait level or feat level adjustments or creations, which seems straightforward.
But now a player wants to start creating their own spell, and I've been trying to pour over the spell-creation mechanics and other homebrew material, and my mileage has varied. Sometimes the rules are straight forward but vague, other times they get byzantine as all get out. The player wants to be able to combine the effects of two spells; blink and fireball. The gist is that he wants a short teleportation adjacent to an enemy and then be able to further 'teleport' the fireball inside the enemy for augmented damage of a fireball.
I've asked him how he wants to limit this so it isn't instantaneous death for enemies, as saves seem appropriate for an effect like this. He says he doesn't want an AoO to trigger in the blink, as he justifies the spell's initiation of effects would be before the teleportation and not trigger one, as well as this effect being 'surprising'. Is this appropriate? Furthermore, he wants no reflex save for the spell as the effect is manifesting inside a creature...I told him how would he feel about a ranged touch attack, and he seem somewhat receptive to this, but he'd obviously prefer to leave all chance from the spell. Obviously, I'm convinced some of the things he wants simply can't be done for balance purposes, but I do want to work with him. He's a 9th level wizard right now, so he's got access to 5th level spells.
So from folks who have navigating making custom spells, how doable do you think a spell like this is? Will it be overpowered? What level spell should we look at making an effect like this and how much damage should it do or what effects should it carry? It seems like making this a 5th level spell might be too high, and making its damage like that of an empowered fireball might seem like a good damage threshold, but thoughts and advice regarding this situation would be deeply appreciated. Like I said, homebrewing spells is entirely new to me, and veterans have probably navigated this before, so any guidance would be super helpful. Thanks so much!
Start by looking for existing spells that have a similiar final result and compare power and level. At first glance I would compare to boil blood, finger of death and polar ray.
Now I totally want to pass somebody a delayed blast fireball as a beguiling gift. And ask them if they'd like a candy...
This sounds like a spell which does massive damage to one target, so as Java Man suggests look for other spells which do that. Finger of Death, Polar Ray now as this suggests both of these are more powerful than 5th level spells.
For lower level Boneshatter does large amounts of internal damage , with a fortitude save and a possible condition.
He will not get a spell which has no save and no attack roll, I believe magic missile is the only exception and that does small amounts of damage , if he wants lots of damage they get a save. As he is going for an internal explosion I would say fortitude save , with it they make the save no proper ignition and a small amount of damage or if they do lots of damage.
Distintigrate may be a parallel and would scale down to 5th level as you don't get the ability to disintigrate walls of force etc.
So Ranged touch, then fortitude save if they make it 5d6 damage if they fail double level in damage d6 i.e at 9th level 18d6