Vital Essence and the Draining of, for Spell Purposes
Vital essence casting risk from the 1979 AD&D Dungeon Masters Guide.
Devitalization
(Mordant Arcana):
The Spellplague had a lasting effect by making a great many spells ranging from a few decades old to ancient sorcery useless and even dangerous. Over the last twenty five years, great effort has been made (with more success than failure) to bring these spells, incantations and rituals back to the population of Grage. Today these spells can be cast in a manageable manner with only a small portion of caster vital essence sacrifice, which is quickly replaced from the immediate area around the spellcaster, but regardless the health of the caster is put in jeopardy.
When casting a spell that has been proven to be Mordant Arcana, the caster must make a constitution save, and on a failure the caster has sacrificed a small measure of lifeforce. The effects are immediate: Until the end of the caster's next round, strength, constitution and charisma saves and checks are made at disadvantage. In addition, all concentration checks to maintain a spell are made with disadvantage for the next 1d3 rounds. With the loss of lifeforce, the caster skin will turn gray with veins and arteries bulging as the skin tightens unnaturally. Most casters turn an ashen gray, hence the slang term "Burning Gray", but in some cases the afflicted spellcaster will turn a gray/ice blue or will blacken to just shy of looking charred. Thankfully the effects from a magic-user casting a spell do not stack*, but another Mordant Arcana spell cannot be cast for the round that devitalization is present.
Echoes of the Spellplague
Grage was struck by the same Spellplague that struck Toril and Abeir, but it was a weaker wave that entered Grage via the newly created Shadowfel (after turning humans into Shadar-Kai) through the Grage "former" Plane of Shadow Astral Gate Deterrent System (poor Gnomes). The effects in comparison to Toril were minimal, with little damage to the environment itself (with the exception of Ahegthna), and the vast majority of races and species escaped becoming plaguechanged with spellscarring only possible on the continent of Ahegthna.
Spellcasting was affected the most, but mainly spells brought to Grage after Boccob reigned as the deity of magic and spells that were altered by a spellcaster from older magic formulae.
Post Spellplague History
The terms Mordant Arcana and Devitalization were coined by the famed gnomish transmuter/artificer Wheezy Dubstepper, who after successfully decoding and casting Glitterdust, turned the palest shade of gray and wheeled backwards from his casting platform, falling into his taffy pulling machine. Wheezy survived his ordeal and informed many other mages, but unfortunately many others went through similar experiences resulting in grevious injury and death. While the gnome did provide a medically viable term, the slang terms burning grey/turning grey are used by most folks today.
The post Spellplague first year had just about every spellcaster attempting to find out which majiks worked, which failed and which would prove fatal if casted. To minimize death and injury, the vast majority of casters and creatures put aside differences to test and record which spells were usable. Even hated enemies collaborated together for a brief time until a quick list of essential spells were found to be safe. After these spells became known, mass collaboration gradually trailed off.
Mordant Arcana
The spells that I have been adding to Homebrew are all considrered Mordant Arcana. Through Devitalization normally does not stack, contamination levels caused by Drakkenheim spells are Mordant Arcana and do stack, but in duration only.
Currently, Mordant Arcana affects mainly spells brought to Grage after Boccob reigned as the deity of magic, and spells that were altered by a spellcaster from older magic formulae.
Devitalization Formula
The caster must make a constitution save, and on a failure the effects are immediate: Until the end of the caster's next round, strength, constitution and charisma saves and checks are made at disadvantage. In addition, all concentration checks to maintain a spell are made with disadvantage for the next 1d3 rounds. The trade off for dealing with Mordant Arcana spells from earlier editions is that the vast majority of these spells do not require concentration.
Drakkenheim Spells
For spells from the Drakkenheim books, we will be replacing the Contamination mechanic with the Devitalization mechanic. Unlike other MA spells, devitalization can stack, and can affect the caster and/or target as described for individual Drakkenheim spells.
I like the contamination mechanic and the mutations and transformations it brings, but with all of the other books and changes the players have to keep track of, we just don't have the time.