Custom divine abilities, portfolios, etc.

[Obly99]

Ok, I will give my feedbacks.
I will start that I will give it a level (or Epic spell or 10th+ like for Netheril Arcanist), not a plot device that the fist elf can invoke because the DM say so.
For casting time i presume you mean 1 standard action (1 action is 5e or PF2e). For Spell Resistance i will say Yes and ST Reflex half (see after for my idea). I go always for the rule of two: a spell must always have at least two between ST, SR, and attack roll.

Description: The caster's eyes go blank, and a massive blizzard blankets the area, with storms of razor-sharp ice crystals shredding the creatures chosen as targets. All targets in the area are killed, ignoring any immunities to death effects, unless they are significantly stronger than the caster. (i.e, about 10 levels/CR's higher for mortals, 3 Divine Ranks above for Immortal casters.) Furthermore, all creatures within a mile of the spell's caster gain total cover for the round after the spell's casting, and are treated as they are in greater magical darkness due to the magical snow.

(This spell cannot be cast as either a prepared or spontaneous spell, it can only be cast in a situation of desperation. This spell is most likely meant for NPC's to use for plot beats, rather than as a direct in-combat spell.)

Ok, I will be blunt. Insta-kill are for me an absolutle no. Also when the effect kill all that is not 10+ levels of the caster even more. I will be ok if it deals 10 cold damage/level with a Reflex half and insta kill for creatures A LOT less powerful than the caster (20 HD lesser than the caster level for mortals and DR 3 lesser for Immortals) with still the Reflex for reduce to instead the full cold damage.

Interesting idea but for me the actual version still need to be polished. In this state I will say that CAN work but only as the ability of a very specific creature important for the campain plot and not as an ability that the first mage capable of casting cantrips can cast if under extreme stress/danger (eg. the elven princess Elsa cursed from birth with uncontrolled power over ice, not Billy the mage novice that still has difficult to cast mage hand)

 

[ArcanistDragonborn]

I fully agree with what you have to say about the spell, it is very much more of a plot device than a spell to be used normally. I will probably edit the spell to change the insta-kill to something similar to what you've written down, and have it require a much stronger magical level of talent/bloodline. Thanks for the feedback!

Edit: I cleaned up the spell and changed it to make it more restrictive and less overpowering.

 

[Obly99]

I fully agree with what you have to say about the spell, it is very much more of a plot device than a spell to be used normally. I will probably edit the spell to change the insta-kill to something similar to what you've written down, and have it require a much stronger magical level of talent/bloodline. Thanks for the feedback!

Edit: I cleaned up the spell and changed it to make it more restrictive and less overpowering.

Much more balanced this new version. Only note is that it's convenient to give a spell level, even a "phantasmal" one for interaction with effects and calculate the DC. Because this is so powerful I suggest that count and work as an Epic spell, so its "level" is 10th and can potentialy overcome anti magic field. Also, the caster level for such spell is equal to the caster level of her spellcasting class or her HD?
PS: You forgot to edit Saving Throw from None to Fortitude half