SUGGESTED EDITS FOR CLARITY:

You shout the command word and one creature of your choice within 30 feet of you must make a DC 18 intelligence (Arcana) saving throw. If they succeed by less than 5, the caster ( or the target? "They" is unclear) chooses from one of the following effects: Take 5d8 Psychic damage, be thrown 60 feet into the air, be poisoned for 5d4 hours, become incapacitated for 4d2 rounds, be teleported to a random plane of existence, or suffer the effects of the geas spell for 1d4 rounds. If target succeeds by 5 or more, there is no effect. If they fail, they take 5d8 psychic damage, and become incapacitated. If they fail by 5 or more, they take 4d8 psychic damage, 4d8 necrotic damage, and are paralyzed from the waist down for 1d4 hours.

(the four different save conditions make this cumbersome to DM... IMHO)

WOAAAAH!!!!

mmm yes, an Arcana saving throw 

if u increase the requirements to cast it, you could prolly make it easier to understand, like simplify it by making it symmetrical. if they pass by more than 5, nothing happens, if less than 5 they choose one, if fail by less than 5, you choose, if more than 5, all happens. it would need to be stronger, but its really weird to give a long list of options for the target to choose, then only use like 2 of them if they fail.