I have developed a homebrew magic item designed to give more choices to a ranged weapon user so that it isn't just attack rolls every round. I think I have a good solution, but I'm inexperienced with the numbers.
I want the extra damage to be consistently 4dX, and I also want the power levels of each choice to be similar. I know that something like the force effect below brings little to the table, but something like the poisoned effect is very strong. I've given my best guess. I am not concerned with the overall power level of the item, just the relative power of the different choices.
What dice should each of the effects below be and why?
Legendary wondrous item, requires attunement
This small side quiver holds 10 arrows or bolts. Each dawn, whatever 10 pieces of ammunition are in the quiver will become enchanted until the next dawn. While an ammunition is enchanted in this way, you can speak a command word corresponding to one of the below enchantments. When the ammunition is launched, it gains that benefit. If the arrow misses, the arrow returns to your bow and remains enchanted, but if it hits, it loses its magic.
Acid. The arrow does 4d6 acid damage in addition to its normal damage. If the target is wearing any armor, it is corroded, causing the enemy to take a -2 penalty to AC while wearing that armor. This penalty cannot reduce the target to below the base value for AC, but can stack with itself.
Cold. The arrow does 4d8 cold damage in addition to its normal damage. The speed of the target is then reduced to 0 for 1 minute. At the end of each of the target's turns, it can make a DC 15 Constitution saving throw, increasing its speed by 10 feet on a success. Once the target has no speed reduction, it is no longer affected.
Fire. The arrow does 4d8 fire damage in addition to its normal damage. At the beginning of each of the target's turns, it takes an additional 2d8 fire damage until it or a creature within 5 feet uses an action to stop the target from burning.
Force. The arrow does 4d12 force damage in addition to its normal damage. If this damage reduces the target to 0 hit points, it is disintegrated. A disintegrated creature and everything it is wearing, except magic items, are reduced to a pile of fine grey dust. The creature can be restored to life only by means of a true ressurection or a wish spell.
Lightning. The arrow does 4d8 lightning damage in addition to its normal damage. Each other creature within 5 feet of the target must make a DC 15 Dexterity saving throw, taking 2d8 damage on a failed save and half that on a successful one.
Necrotic. The arrow does 4d6 necrotic damage in addition to its normal damage. The target has disadvantage on Strength, Dexterity, and Constitution saving throws for 1 minute.
Poison. The arrow does 4d4 poison damage in addition to its normal damage. The target then becomes poisoned for 1 minute. While poisoned in this way, whenever the target attempts to take an action, they must make a DC 15 Constitution saving throw, spending their action vomiting on a fail. On three successes, the target is no longer poisoned.
Psychic. The arrow does 4d6 psychic damage in addition to its normal damage. The target has disadvantage on Wisdom, Intelligence, and Charisma saving throws for 1 minute.
Radiant. The arrow does 4d8 radiant damage in addition to its normal damage. For 1 minute, the target has a sparkling silhouette that removes the benefits of invisibility and gives advantage on all attack rolls against the target.
Thunder. The arrow does 4d10 thunder damage in addition to its normal damage. The target is deafened for 1 minute and pushed 30 feet in the direction the arrow was traveling.