Requirements for the spell (IRL). Secondary figurines as well as, if the Dm chooses, a secondary game surface. (i suggest keeping the secondary figurines and surface white to aid in time spent making the set as well as to add to the role play, as this secondary set is the illusion brought upon by the caster.) Considering the momentous nature of the spell and the high potential for it ending in campaign death for the caster, i believe its a worth while effort to make.
The Forbidden Spell (the forbidden spell)
The caster must use an action to begin the spell casting process. The caster must sit on the ground and meditate with a single gold piece within each hand until their next turn, if the caster completes the visualisation and secures the gold coins in their palms without dropping them (if they take damage between their turns have them make a constitution saving throw of 8 or higher to retain the coins) it will then cause the spell to take full effect. If the coins are dropped at any point then the spell does not succeed. The spell causes all that are within its range to freeze and experience a simulation of reality for the next 3 rounds (this includes allies), during which time, the caster may move a maximum of 20 feet in any direction and complete its next 5 turns in the real world (with their movement encumbered to 20 feet per round due to the real world mental stress of the spell, this encumberment does not apply to the illusion). the spell ends after the next 5 rounds are completed in both the real world and that of the illusion. During the spell, the coins will be burned into the palms of the casters hands, meaning that they can handle equipment (weapons, potions, miscellanious etc) however must make a constitution saving throw of 8 or higher to determine their effectiveness in combat post casting. (any lower, all attack roles receive -2 modifier.)
(DM's choice) The Illusion realm (the Illusion Realm)
Everyone within the 60 feet range of the spell experiences a set illusion. In this illusion, play resumes as normal however the caster must role a d4 in order to modify the roles of each party. The player roles twice, the lower of the two is used as an additional plus modifier for those the caster deems a friend, the higher of the two roles is used as and additional negative modifier for all those that the caster deems an enemy. During these rounds the caster receives two turns, the first of which being for the casters Illusion self and the second of which being for the casters real world self. The illusion ends once all 5 rounds, including the casters additional turns are complete. At the completion of the spell, those who the spell caster has deemed as an enemy will then receive all damage potentially caused by the caster in the real world AS WELL AS retaining all the damage received in the illusion, however, all those who the caster deemed a friend will only be dealt damage that they receive in the real world. Meaning if they die in the illusion, they do not die in the real.
The Cost of Power (The Cost of Power)
However, After the spells completion the player will role a 7+d20 to determine how much psychic damage is taken. Regardless of ending Hp level, the caster is then unconscious for the next 24 hours. Party members are unable to heal the caster in anyway shape or form. The caster must then make his or her saving throws AFTER the 24 hours have elapsed in game. with a -2 modifier, normal rules then apply.
The Death Script (the death script)
If the caster does indeed perish, then the gold in their hands will deteriate, and crystalise over the casters eyes before the caster circums to his or her injuries.
The Further Cost (the further cost)
If the caster survives, upon waking, the coins will burn the casters palms leaving permanent golden scares, before deteriating. The player will then hear a voice say, "your journey is payed for." It may be up to the discretion of the DM but for the rest of the campaign, the caster will have one main stat (strength, dexterity, constitution, intelligence, wisdom, charisma) will decrease by 1.
* - (2 gp, "The Scroll of The Forbidden Spell" (the scroll informs the player of the spell, it is not used in the spells performance))