Looking for non-overpowered spell-like effects on a weapon instead of +1 weapon [closed]

Question

Starting a 4-5 level rogue, D&D 5e.

Problem to solve: a magical spell-like effect to put on a weapon, instead the standard +1 weapon, with a rarity of uncommon. It is unclear what can or should be applied within the above constraints to prevent being overpowered for that level.

1d4 poison, fire, ice damage seems about right, or can 1d6 fit within the above limits? Also, should the damage be applied 3 times per day (charges) or on every successful hit?

Will a magical effect of "extra sneak attack damage dice" be overpowered for this level?

Alternately, would adding a cantrip spell effect, such as booming blade or green-flame blade, fit the limits of being uncommon/level 4-5 appropriate?

If so, would the limit of once per short rest or 3x per day fit the same limits?

I don't have a feel for what is OP, what is underpowered, or what is silly.
I can always get an uncommon item.

Answer 1

Adding 1d4 damage to the weapon would be a similar effect

Challege with the Question

The challenge with this question is that, the power a +1 weapon in terms of the average additional damage varies depending on a large number of factors:

• What type of weapon is it? (Higher damage weapons get more benefit from +1 to hit)
• What is the characters attack bonus? (a higher attack bonus makes the +1 to hit less valuable)
• Are you attacking with advantage / disadvantage? (More useful if you have disadvantage and less useful with advantage)
• Are you dealing sneak attack damage? Are you an assassin with auto-crit possibility? (Both of these make the value of a +1 to hit higher)

Value of a +1 Weapon

Given the above, I am going to make a series of assumptions in my answer, let me know in the comments if you think these are wrong / unreasonable:

• You are a level 4 rogue
• Your Dex modifier is +4 and proficiency bonus if +2
• You are using a rapier as your weapon dealing 1d8 + 4 damage on a hit
• You are getting sneak attack on 50% of your attacks
• You are fighting enemies with an average AC of 13
• You have neither advantage or disadvantage

Based on this:

The average damage that you deal with a normal rapier will be 8.8

The average damage that you will deal with a +1 rapier will be 10.15

So in terms of damage output, the +1 weapon increases your damage output by 1.35 per attack.

Comparing with Other Effects

1d4 to Every Roll

If instead of a +1 weapon you added 1d4 of damage to every roll, this would increase the average damage by 1.875 so this would be marginally stronger than a +1 weapon. If you picked a damage type (e.g. Fire) which is commonly resisted then this would be a reasonably comparable weapon

Higher damage dice

If you are using a higher damage dice, this quickly becomes much stronger. Even a 1d6 means that the damage is 2.625 higher than the base weapon which is double the benefit of a +1 weapon. So if using a higher damage dice, I would say you should limit the effect to a fixed number of uses per day. The higher the dice, the fewer uses it should have.

Other spell effect

I am not going to detail all the spell effects and their relative benefits, but for any proposed effect I would recommend looking at the expected impact on damage (or the battle in general) and seeing how this compares to the impact of the +1 weapon.

You can also look at other magical items which produce spell effects and see the rarity of these items. This should give you a steer on whether or not the effect is overpowered.

Answer 2

Two reskinned magical items fit your needs

To offer a choice, here is a reskinning for either a "nova" or a "sustained" damage uncommon magical item. From the uncommon magic items in the DMG two items fit, but need to be reskinned to suit your rogue's desires.

1. Storm Sword (uncommon)
   This is a reskin of the javelin of lightning in the form of a short sword.

   This magical short sword, when you speak its command word, releases a burst of lightning. When this power is used during an attack (whether the attack roll was successful or not) your target must make a DC 13 Dexterity saving throw, taking 4d6 lightning damage on a failed save. If the attack roll was successful, the target also takes normal damage from the sword as lightning damage. The sword's property can't be used again until the next dawn. In the meantime, the sword can still be used as a magic weapon.

2. Backstabber's Blade uncommon (requires attunement)

   This is a reskin of the bracers of archery in the form of a sword.

   While attuned to this sword, you have proficiency with both longsword and short sword, and you gain +2 bonus to damage rolls on attacks made with this weapon.

   I'd recommend keeping this on a short sword, a rapier, or a dagger to ensure that you still get your sneak attack bonus. This isn't as much as one added sneak attack die (2 versus 3.5 damage boost) but it's a damage boost to any and every hit you make.

Work with your DM on the final details.