Which of these two magic daggers is better for my rogue?

Question

My rogue with 34hp just found a new dagger for the first time. Being new to D&D, I was filled with excitement for my first new weapon. Then I really read the card and now I'm thinking my old store-bought 1d4 + 1d6 fire dagger (needs Attunement) is still better.

Scarlet

Dagger, rare (attunement by rogue)

As a bonus action you can imbue the red raded blade with your blood dealing 1d10 necrotic damage to yourself, which cannot be healed. When the blade is imbued with your blood you gain the Aura of Scarlet the Bloodraven. The Aura lasts for 1 minute and can be cast 2 times a day recharged at a long rest.

When affected by the aura, your sneak attack damage can be come necrotic damage, or poison damage.
You gain plus 1 to your AC
You gain resistance to necrotic damage
When you are attacked by a hostile creature you can target that creature with the Bloodravens curse. You deal an extra 1d4 necrotic damage to that creature, and can impose disadvantage on that creatures perception checks on you.

Scarlet is a +1 weapon, but with a 1 min time limit and the fact I have to be targeted and the chance to lose 1/3 of my health permanently for a day.

Am I missing something or is this weapon kinda lacking and more of a cursed item I need to get rid of? Am I better off with my old flame dagger or the new Scarlet dagger? I still don't know a lot about D&D and magic items — I'm hoping to get advice from more experienced players. Use Scarlet? Try sell it? Etc.

Answer 1

Short answer: Probably not worth it.

In general, while the aura has some interesting effects, it costs too much to activate, probably.

Necrotic resistance and +1 AC are pretty decent, and the curse is ... well, it's okay. But since your existing blade does better damage already (is your existing blade +1?), all that leaves is being able to stop attackers from finding you when you hide.

The ability to change the damage type of sneak damage is pretty nearly irrelevant. The weapon is magical, so it already overcomes most sources of resistance or immunity to stabby damage. So unless the target is vulnerable to poison/necrotic (very rare), or resists magical stabby damage but not poison/necrotic (also very rare), I don't see much point to that.

Here's what I'd suggest:

Rogues benefit from dual-wield. Use your existing fire dagger as your main-hand weapon. If you hit with it and deal sneak damage, great. If you miss, you can spend your bonus action to attack with Scarlet and try to get your sneak damage anyway. Just use it as a +1 dagger.

Once in a blue moon, maybe you get into a bad spot and do the blood aura thing to try to improve your chances of escape, but most likely you never use the dagger's full potential.

But:

The imbue vs cast thing isn't very clear (I assume the DM meant them to be synonymous), and it doesn't say when the damage can be healed. Does the DM mean it can't be healed while the aura lasts? Because that's not so bad, you can get cured after the fight is over. If it really is for the rest of the day or something, then no, I'd never use the dagger's blood power.

Talk to your DM about your concerns.

If he gave you a 'cool artifact' weapon, he obviously expects you to use it, and if you feel it's too much of a risk to ever use, he may be willing to work with you on it. See if he'd be willing to cut down the aura's cost a bit, like make it a d6 damage so it's a little less risky to a squishy rogue. Or have the aura give you resistance to all damage instead of just necrotic, so you're taking damage now in hopes of taking less damage later.

Just some ideas.

Answer 2

This item is considerably worse than your existing dagger, and here are the numbers to prove it.

Flaming dagger

Your base damage is around 1d4+3 (average 5.5) or 1d4+3+2d6 with sneak attack (average 12.5), assuming you're about level 3. Flaming adds 1d6 (average 3.5) against any non fire-resistant enemies (and fire resistance is rare), increasing your damage output by 64% without sneak attack, or 28% with sneak attack.

Scarlet

First, you're giving up the flaming dagger, which costs you around 22% - 39% of your former damage output, depending on sneak vs no-sneak.

As written, this item isn't a +1 item. In 3rd edition, magic weapons were generally at least +1, but this isn't the case in 5th edition. If it actually is a +1 weapon without being listed as such on the card, it makes you approximately 5% more likely to hit and deal damage (not exactly, but this is approximately true over a range of ACs) and increases your damage when you do hit by 8-18%, for a rough damage increase of 13-24%. This is considerably weaker than your flaming weapon, which gave 28-64%.

Assuming I'm reading the card correctly, all of Scarlet's abilities only activate when you pay the hit point cost. That cost is approximately 16% or one sixth of your current maximum, on average, and is roughly equivalent to taking a hit in combat. Of the benefits you do get:

• Switching your damage type is not a powerful ability. It's very rarely useful, and only against a creature who is resistant to normal weapons but not necrotic/poison, or who have some weakness to those types. As a newbie player you have no way of knowing which creatures those are, and reading the Monster Manual to find out is traditionally considered against the spirit of the game.
• +1 AC is pointless, because you had to take the equivalent of one hit already to gain this ability. You would be better off not injuring yourself to begin with. +1 AC will, approximately, save you from one hit in twenty, and it only works for one minute (ten rounds). On average, if you take enough hits for the AC bonus to save you more than the dagger dealt you, you're already dead.
• Necrotic resistance is useful against specific enemies, but again, it's weak because you had to intentionally take damage in order to gain this damage resistance. It's also hard for a player to know in advance which creatures deal necrotic damage, since many undead simply deal normal damage. And most creatures don't deal necrotic at all, so most of the time you use this weapon, this ability won't help.
• Bloodraven's Curse requires an enemy to attack you. +1d4 damage is beneficial, but it's still less than the 1d6 damage your flaming dagger was doing, and only works against the opponent attacking you, which means it only applies to a limited subset of attacks you make, and doesn't apply when you're attacking from hidden. Your target has disadvantage on perception checks, but that's pointless because it has already seen you, and you can't hide from them again mid-combat.

In short, the abilities of this item are straight up weaker than your existing flaming dagger, and the additional hit point cost is not worth it. And since it can only be used twice per day and for limited duration, you will spend a significant amount of time with a dagger that has no special properties.