D&D 5E Karakan

[Cap'n Kobold]

Would this suffice?
"When you become attuned to or wield Karakan, you must make a Charisma saving throw against a DC of 12 + the number of days it has gone unfed. If you fail, you become overcome by bloodlust, and must attack the nearest creature each turn. You can end the bloodlust by bathing the blade in blood as an action."

So if you pick it up out of an old hoard for example, the first time that you take a swing with it, you'll probably need to make a Charisma save with a DC of several hundred thousand?
Does the wielder automatically know how to stop the bloodlust? Or only when attuned?
What are the mechanics of "bathing" the blade in blood? Do you need an incapacitated or dead foe? How much damage do you take if you choose to use your own?

Functionally, Heavy on a one-handed weapon is worth the +2 AC. That's pretty close to balancing with a +3 to it and damage: moreso when you take the +d6 damage into account.
When balancing weapons, you need to take into account who will be using it. Granting Heavy to a longsword isn't locking out Dex and sneak attack because someone who uses sneak attack/Dex/is small wouldn't be using it. You balance it based upon someone who can use it to advantage unless you know that the group to whom you are giving it to won't have anyone in it who can.

(Just consider how nasty this weapon would be after a warrior-type has it and builds around it. Combining GWM, +2 AC and Shield Master for example.)

 

[Yunru]

So if you pick it up out of an old hoard for example, the first time that you take a swing with it, you'll probably need to make a Charisma save with a DC of several hundred thousand?
Does the wielder automatically know how to stop the bloodlust? Or only when attuned?
What are the mechanics of "bathing" the blade in blood? Do you need an incapacitated or dead foe? How much damage do you take if you choose to use your own?

Functionally, Heavy on a one-handed weapon is worth the +2 AC. That's pretty close to balancing with a +3 to it and damage: moreso when you take the +d6 damage into account.
When balancing weapons, you need to take into account who will be using it. Granting Heavy to a longsword isn't locking out Dex and sneak attack because someone who uses sneak attack/Dex/is small wouldn't be using it. You balance it based upon someone who can use it to advantage unless you know that the group to whom you are giving it to won't have anyone in it who can.

(Just consider how nasty this weapon would be after a warrior-type has it and builds around it. Combining GWM, +2 AC and Shield Master for example.)

Eurgh, this is really making me hate writing out custom items
Yes, it's likely to have an auto-fail first time you attune, but it's not supposed to when you first wield it, because you're not supposed to be able to wield it without being attuned (which I forgot to include).

For bathing it in blood, it's up to the DM. But I would say just covering the blade is enough. If you choose to use your own? Hmm... I think I'd go for the weapon's damage.

Your right about Heavy. I was thinking about it from the other way round: A Sword 'n' Boarder can get GWF. Right, Very Rare it is.

 

[Yunru]

So if you pick it up out of an old hoard for example, the first time that you take a swing with it, you'll probably need to make a Charisma save with a DC of several hundred thousand?

Another fun way to drop it is to have it in an encounter room, and have one of the enemies pick it up mid-battle (for a cursed auto-attunement variant or something).

"The goblin lunges for the sword, grabbing it and pulling it free of its resting place. A crazed smile appears on his face as his eyes cloud over. He lunges, swinging for his fellow Goblin."


For other random titbits: Karakan is loosely based on Tyrfing.

 

[Istbor]

I think the clutter is mostly because Sentient Magical Items aren't well laid out, although I could see it being bumped up to very rare (depending on how much being Sentient (but not Sapient) counts).

For the ability, I may (read: will) rework the wording then.

Would this suffice?
"When you become attuned to or wield Karakan, you must make a Charisma saving throw against a DC of 12 + the number of days it has gone unfed. If you fail, you become overcome by bloodlust, and must attack the nearest creature each turn. You can end the bloodlust by bathing the blade in blood as an action."

Yeah. I think that wording works. I thought for a moment that it should force the DC before attunement but then thought better of it. I mean, how would you know then to bathe the blade then? Probably think is it just an evil cursed blade and lock it back up.

I too am uncertain how much weight a sentient weapon should carry regarding the rarity. I think OotA has one, that you can get somewhat early on, but do not recall if it is rare, very rare or more. I tend to start at very rare myself with items that have personality and can communicate though. Since I feel a vast amount of time, and incredible events had to take place to create that sentience. Again, that is me, others may see it differently.