Here's another spell for Raggi's Weird Magic system, introduced in his 2017 Free RPG day submission. It uses the system described therein. If you don't have it, or don't want to use it, just make this a first level magic-user spell. Raggi's Weird Magic can only be cast by females; use or discard this restriction as you see fit.
As with Raggi's spells and my previous offerings this year, the spell is named after a death metal song.*
When the Sun Rises for the Last Time
This spell literally causes the end of the world.
First off, the caster must gather a congress of 101 sentient beings, not including herself. She must inform them, in no vague or uncertain terms, of her intent to immediately bring about the end of the world and the obliteration of all sentient beings. The 101 there gathered must agree unanimously. Among the 101 there must be at least one elf, dwarf, halfling, or whatever 'major' races appear in your campaign. If you do not use nonhuman characters, there must be representatives from at least four nations. There must be at least three clerics of different faiths, none of whom count toward the race/nationality requirement.
The members of this congress must agree of their own free will; they cannot be under magical or psychic mind control, nor can they have been coerced into agreement. They must willingly understand the choice they are making and the ramifications thereof, so it's not possible to use children or the mentally unsound. If even one member of the congress disagrees or agrees under some sort of pressure or compulsion, the spell fails and you must immediately roll on the failure table twice and take the worst result. If you don't use the Weird Magic system, just give the caster a level drain or have her head explode or whatever fitting punishment the DM comes up with.
The spell must be cast at sunrise, with the entire congress within 300 feet of the caster. It otherwise fails to function.
If the spell is successfully cast, the game world has one day before the world ends. It unfolds in the following sequence:
1. All members of the congress, and the caster, immediately die. Their souls are completely obliterated and nothing can restore them to any semblance of life. They cannot be animated as undead. They likewise do not proceed to any afterlife that may exist.
2. Cleric spells cease to function globally.
3. All beings in the region understand that this is the last sunrise, that the world will end in a day. They don't know how they know, but it is certain. They will feel a compulsion to complete the one thing they most want to do in the next day and will do anything in their power to make it happen. Obviously it must be a desire that can be fulfilled in the next day. If they have no such desires, they simply seek to make the most of their last day: spending it with loved ones, eating favorite foods, etc .If an individual desires to resist this for some reason, they may save vs. Magic, with success allowing them to act as they please.
4. Just before the next sunrise in each region, living animals and humanoids turn into pillars of salt. Plant life withers into blackened husks. Undead crumble to dust or dissolve. Self-aware but nonliving things become inanimate shells. Food and forms of sustenance rot.
5. After the living things in a region die, all man-made structures in the region crumble to ruin.
At the terminus of the spell, the entire planet is devoid of life, a crumbled graveyard from pole to pole. The dead planet will continue to orbit its star until said star goes nova. (This spell does not hasten the end of the star)
There is no way to stop this spell once it has successfully been set in motion. The only way to escape the apocalypse is to somehow leave the planet or the plane of existence. Return at a later time is certainly possible if the individual has the means to do so.
Weird Magic Failure Table:
1- Nothing happens, and this spell is erased from existence. All scrolls crumble, pages in spellbooks are rendered blank, and it is wiped from the mind of the caster and anybody else in the world who happens to know it. Attempts to research this spell, or to create one similar to it, automatically fail. Additionally, all clerics the world over know the caster's identity and that she tried to end the world with magic.
2- As above, but the clerics of the world do not gain any special knowledge or even know that anything happened. (The spell is just obliterated from the world)
3- The caster and the congress die, but the spell does not otherwise function.
4- The congress and the caster still die, but the world doesn't end and magic isn't affected. However, all beings the world over experience a feeling of peaceful contentment for 24 hours, and all fighting everywhere stops. Normal emotions and conflicts resume in each reason as the sun rises, though individuals remember this feeling of contentment and may or may not desire to return to it.
5- The spell functions normally, but the caster does not die, nor does she become a pillar of salt. She becomes the sole inhabitant of the world. In addition, she no longer needs food or water, and in fact cannot die. She loses all ability to use magic or magical items. She is left to wander an empty world alone. If somehow rescued from the planet, these consequences do not fade and cannot be in any way reversed.
6- The congress and the caster still die, but time is frozen. The planet remains fixed in place, and all regions will experience whatever time and weather conditions presently exist there forever. (Sunrise at the origin of the spell, winter where it's snowing, etc) Clerical magic still works. Spells that alter time or weather no longer function. (haste, call lightning, etc)
7+ - Roll a d6 and consult the chart above. Failing at this spell does not incur lesser consequences.
*I had to look up death metal song titles on the internet, as I don't listen to death metal and am not familiar with bands or songs of that genre.