Earth Splitting Event Help

I've been meaning to tinker with 5e mechanics, so lets make this an exercise in Epic Level Spells.

Per 3.5, an epic spell is developed from raw elements of magic called 'seeds' and connecting pieces called 'factors'. Every epic seed has a base DC, and every factor has a DC adjustment. When an epic spell is developed, the spellcaster spends resources and time to assemble the pieces that make up the epic spell. The base DCs of each seed are added together; then the DC adjustments of the factors are added to that total. The sum equals the final DC for the epic spell.



Storm of Vengeance DC 25
Earthquake DC 23
+900% area +36 DC
84 DC total

Monetary Cost: The development of an epic spell uses up raw materials costing a number of gp equal to 9000 x the final DC of the epic spell under development.
Development Time: Developing an epic spell takes one day for each 50k gp, rounded up to whole days.
XP Cost: To develop an epic spell, a caster must spend 1/25 of its resource price in experience points.


To cast an epic spell, a spellcaster makes a check against the epic spell's DC. If the check succeeds, the spell is cast. If the caster fails teh check, the epic spell fizzles and is lost.



Additional participants: You can develop epic spells specifically to require additional participants (sometimes called celebrants). Epic spellcasters might call such an epic spell a cooperative spell, a mythal, or a ceremonial spell. An epic spell developed as a ritual requires a specific number of additional participants, who each must use up one spell slot or a specified level for the day. During an epic spells development, the spell's creator determines the number of additional participants and the level of the spell slots to be contributed. If the exact number of spell casters does not partake in the casting, or if the casters do not each contribute the proper spell slot, the epic spell automatically fails. To participate, each celebrant readies an action to cintribute his or her raaw spell energy when the primary caster beings the epic spell.
Additional participants in a ritual spell reduce the DC. Each additional participant may only contribute one spell slot. It doesn't matter whether the additional participants are arcane or divine spellcasters; only the level of the spell slot contributed matters.
A contributed spell slot is treated as if normally cast.

Spell slot level contribute
1      -1  DC
2      -3  DC
3      -5  DC
4      -7  DC
5      -9  DC
6      -11 DC
7      -13 DC
8      -15 DC
9      -17 DC


A ritual epic spell requires all extra participants to stand as if casting for the same amount of time. If an extra participant is attacked while contributing a spell slot, the participant must make a Concentration check. If the attack disrupts the participant in the ritual, the epic spell is not necessarily ruined. However, the Spellcraft DC reduction that would have been provided by that additional participant cannot be applied to the final Spellcraft DC of the epic spell. Thus the ritual epic spell will be harder for the primary spell caster to cast.
Cast time + 1 minute -2 (max -20)
Cast time + 1 day -2 (max 100 days)




The above describes a Storm of Vengeance combined with Earthquake. I expanded the area from 360' to a full km. If the effect is several kilometers long, then the base DC would be +40 per extra kilometer. The extra costs to develop the spell and the efforts to mitigate its difficulty would also be greater. It is considered a ritual, its duration is 20 hours, and the DC for its effects are DC 30.

I think the point of Epic Spells, when designed by the game authors, was to make up mechanics that require story and plotting to cast the spells. They do, by definition, break the game and so shouldn't be easily accomplished.

There's a lot you could do if some nefarious villain discovered the notes and wanted to recreate the spell. Perhaps they devise some machine to extract XP from unwilling victims to fuel the development or casting (-1 DC per 100 xp). Maybe an gnome starts an academy of magic so that the full student body can contribute to the casting, each with a 1st level spell. Could even be, someone wants to make the entire effect permanent (total DCx5).

Anyway, that's how 3.5 would do it. I think the above makes sense for 5e as well.