Chaos Crystal (5e Trap)
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This looks like a large ruby, diamond, or other rare carved gemstone sitting on a pedestal. A person may make a Arcana check with a DC of 15 to discover that is not just a gemstone. It creates a 30 feet sphere of chaos. Roll a D8 (or decide for yourself) to decide the ability of this aura. The effect ends if dispel Magic is used, or the gemstone is shattered. A person who breaks the crystal gains a 5 feet sphere of the crystals effect until there next long rest. 1 = Wild Magic. 2 = Limbo. 3 = Gateway. 4 = Transmutation. 5 = Form is irrelevant. 6 = Elemental Chaos. 7 = Spell Aura. 8 = Roll twice more to choose 2 effects. Any Polymorph forms are chosen randomly, unless the effect says they cast it on themselves.
Within this aura, every initiative of 10, or every five seconds out of combat, roll a D100 to choose a Wild Magic effect from the sorcerer Wild Magic table, or from another random table of your choice.
The area within the aura is constantly changing, shifting, moving... The zone within the aura follows the Limbo plane rules.
Every D4 rounds, or every 30 seconds out of combat, a dimensional shift occurs. Roll a D4. 1 = Roll to choose a random creature to summon within the range. That creature disappears if it leaves the range or if th effect ends. 2 = Roll a D4. Starting from the crystal and going outwards, choose creatures to warp to a random area within 30 feet, going to the number rolled. 3 = Open a portal to a random plane of existence. The portal disappears after D20 minutes. 4 = Every creature in the auras range is teleported into a miniature demiplane inside the crystal. Each creature is shrunken to fit inside a small area inside the crystal, which becomes 20 feet for them. Each turn a creature spends inside the demiplane, they can make a DC 20 Charisma check to escape, in which they a teleported back to their starting location outside the crystal, and over the course of D12 Hours, they steadily grow back to their normal size, equipment included. If the crystal is shattered then, each creature inside the crystal regains their size over D20 Hours.
Every D6 Rounds, or one minute out of combat, a wave of transmutation occurs. Roll a D8. 1 = Reduce. 2 = Enlarge. 3 = Leap. 4 = Polymorph. 5 = Any non-worn or carrier object animated. 6 = Fly. 7 = Triple creatures walk speed. 8 = Reroll twice to do a combination effect. All of these spells/effects affect all creatures in the radius for D8 Rounds. If a creature leaves the radius of the aura, the effects end immediately.
Form is irrelevant
A creature within the aura can use their action to transform. Roll a D4. 1 = The creature becomes a shapeless blob and takes D10 acid damage. 2 = Roll a D4. 1 = Polymorph, 2 = Enlarge, 3 = Reduce, and 4 = Nothing. 3 = The creature can cast Polymorph and choose their form, or enlarge/reduce themselves. 4 = The creature can cast any transmutation spell that effects only them. A creature transformed by any of these effects can use a bonus action to return to normal form.
A storm of elements rages in the aura. Every D4 rounds, roll a D4. 1 = A random Elemental is summoned. 2 = All creatures in the radius take D8 damage. Randomly choose damage from fire, ice, or bludgeoning. 3 = A flood of elemental power floods the radius. Randomly choose a effect from a tidal wave, a set stone spikes, a blazing fire, or a icy tornado to form within the aura. 4 = D4 Creatures in the aura become temporary quazite elementals. They stay this way until they leave the aura.
Choose a random spell. Any creatures that enter the area are afflicted by it, or, if it is a area spell (like cloud of daggers, or meteor shower), it stays active in the zone permanently, or until the crystal is destroyed,