Custom spell for home game . Could use some advice

[satio of the Steel Fang]

I plan to run a dungeon adventure and I'm looking at creating unique items as treasures in each dugeon

1 is an old tattered and worn grimore that will teach a new Spell

I want it to be flavorful balanced but still useful

My idea is a cone based attack that inflicts 1D6 points of damage per caster level max 15D6 inflicting slashing damage that over comes both magic and slashing DR and must be casted with a slashing weapon in hand as part of the cost . A non magical.weapon shatters on activation of the spell. But if used with a magical weapon there is an additonal effect, anything that takes damage from spell suffers bleed damage = To crit multiplier of weapon used as focus for the spell.

I know its nothing major but I'd like to work it out as a 4th level spell not sure the school

I plan to create several custom spells and items as relics from the worlds Long forgotten past and special rewards for the players

[Azothath]

offhand - look at retooling Diamond Spray using a slashing weapon as the material component. The spray will have the same material type as the weapon. Base damage upon weapon cost. See Coin Shot.

[OmniMage]

This will probably be a 5th level spell. This for a multi target spell that would deal a maximum of 15d6 damage. If this is a wizard spell, then they would be able to cast it at level 9.

A Cone of Cold is a 5th level spell that does most of the things you want your new spell to do. Change it so it deals slashing damage instead of cold. It doesn't do bleed damage though, so you might want to bump up the spell to level 6 (requiring a 11th level caster).

Material component could be a normal slashing weapon. However, I think you aught to make it a focus instead. Require that it be a masterwork or magic weapon. Not just for my taste, but I think non magical weapons would be cheap and easy to carry for a 9th level adventurer (see bags of holding and handy haversacks). Just need to remember to collect 'spell components' after battle. So consuming the non magical weapon during spell casting would be only good for flavor as they don't really cost anything meaningful at that level.

Maybe the bleed damage for using a magic weapon as focus could inflict the enhancement bonus as the amount of bleed damage the targets take. So a +1 sword would inflict 1 bleed damage while a +5 would inflict 5 bleed damage. This would give incentive to upgrade your focus. Using a crit multiplier instead would make the focus cost 2300 gp (magic + masterwork) + x gp for the non magical non masterwork component. A dagger would cost 1 gp for x2 multiplier, a battle axe would cost 10 gp for a x3 multiplier, and a scythe would cost 18 gp for a x4 multiplier (to list common weapons).

[Pizza Lord]

I would likely not link any bleed damage to the crit multiplier. It's an interesting and unique mechanic, but ultimately unless the caster just has a favored slashing weapon they're holding or can't change weapons, they'll always go for a high one. Like OmniMage said, assuming that the caster is trying to decide what to use for the component, its 2,300 gp for a magical slashing weapon. Are they just gonna spend 2 gp for a dagger (x2) or 4 gold for a light pick (x4) (that's about the lightest and cheapest x4).

Linking it to the enhancement bonus is a better choice. This probably works great for magus or other martial casters. I assume that a successful Reflex save for half also negates the bleed.

[Dragonchess Player]

I would also recommend using the optional Words of Power system to help benchmark spells. Then compare with existing spells for effects and details that don't 100% match the wordspells.

[Azothath]

two general constraints on spells;
1) material components are usually not expensive running 0-25gp, and most manufactured weapons are in that range. Special materials can increase the costs to thousands and that's a scalability issue. Same with magic but it's worse with higher scalars. How do you balance effect with cost??? How do you handle weapons (at low cost) for diminutive creatures being used by a medium sized creature as a spell component (in a working the rules foray)?
Coin Shot with it's obvious material component does this well and creates special material effects. Same with Pellet Blast.
You also have to ensure Eschew Components or False Focus doesn't get around your balancing act. (I don't have a problem destroying a false focus in a sacrificial casting but the player might... and again you want cost to relate to effect)

2) foci are essentially a higher cost gateway mcguffin to cast the spell (and it fills a hand which is not usually a concern). Getting it out hits action economy whereas just having it on you does not.

You can use both but it makes the casting rather difficult.

Just use a standard dice cap and scaling per the spell level. You can break it up into 2 or 3 spells with higher caps.

[thorin001]

1) 5th level seems more appropriate as cone of cold is very similar.
2) I would change the weapon to a focus. I would also have the DR overcome based on the properties of the weapon, so a magic weapon overcomes DR magic, a cold iron weaopn overcomes DR cold iron, and so on.