Chaos Warp

You attempt to interrupt a creature in the process of casting a spell. The creature makes a Constitution saving throw. On a failed save, the spell dissipates with no effect, and the action, Bonus Action, or Reaction used to cast it is wasted. If that spell was cast with a spell slot, the slot isn’t expended.

when you successfully dissipate a caster’s spell this way a random magical effect takes its place. Roll a d20 to determine the effect from the list below:

1. The spell’s energy finds its intended target dealing 5d8 psychic damage. (if there was more than one target a target is chosen at random from the intended targets.)
2. 1d10 bubbles emanate from the target in a 60ft radius. Upon bursting they cast Prestidigitation which magically clean all surfaces in a 5ft radius 
3. For the next 1d10 minutes there is no visible color in a 1 mile radius.
4. The nearest CR 1/2 or lower monster is teleported to a random space within 60ft of the caster.
5. 10d10 crabs are summoned.
6. 1d10 good berries appear in the caster’s hand.
7. the spell is transformed into Plant Growth emanating from their location which lasts for 1d6 minutes.
8. The caster spell is transformed into Create or Destroy Water.
9. For the next 1d4 rounds the caster may wild shape into their choice of a bat, cat, or swarm of insects.
10. A goat appears within 10 ft of the caster.
11. Each person within 60 ft of the caster is pulled 10 ft closer. 
12. The caster grows an octopus arm from their back which remains for 1d6 rounds.
13. Edible quality mushrooms grow rapidly in a 20ft radius of the caster.
14. The caster vomits up gold coins equal to 1d10 times the spell’s level.
15. The caster casts a different spell they know of lesser level instead of the chosen spell if they can’t then they cast fire bolt.
16. For 1d10 rounds The caster gains a fly speed of 30 ft.
17. For the next 1d4 minutes the caster can only speak in rhymes.
18. The caster casts darkness emanating from their position. This doesn’t require concentration and lasts 1 minute or until dispelled.
19. The chaos magic manifests an earth elemental in an unoccupied space within 20 ft of the caster for 1d4 rounds. Your DM decides any actions it takes (if any).
20. The spell backfires on the caster. They take 5d8 force damage and are pushed 5ft back from the blow.