Question: This item seems to have two somewhat contradictory statements in it:
(1) "If you are proficient with shortswords or longswords, you are proficient with the sun blade."

and

(2) "Proficiency with a longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it."

Doesn't statement #1 ALONE IMPLY that you would add your proficiency score to the attack roll if you were PROFICIENT with either a SHORTSWORD or a LONGSWORD? Then why add statement #2 at all? and... more importantly, why does statement #2 partially CONTRADICT statement #1

So.... If you are "proficient with a shortsword" are you proficient with sun blade or not?

AND.... IT'S A BIG DEAL.... because.....while we are on that topic... It further states that "this magic longsword has the finesse property" ! Sooo..... does this imply that a character who normally only uses SHORTSWORDS with DEXTERITY (not strength) can now suddenly use this LONGSWORD as a LONGSWORD, but using their DEXTERITY for the attack, taking advantage of a longsword's 1d8 slashing damage one handed.... and 1d10 slashing damage TWO HANDED!?? And on top of that you add +2 to hit AND +2 damage? (Plus 1d8 damage on top of that to Undead!?)   THAT is GREAT for someone who normally USES a LONGSWORD (with strength) but CRAZY GREAT weapon for someone who normally CAN'T use a longsword, but only uses short sword.... Um.... Imagine taking away a dexterity-users shortsword that normally does 1d6+dex damage, and replacing it with a two-handed longsword that can do 1d10+dex+2+1d8 to undead..... You went from an average damage of 3.5 + dex.... to 7.5 + dex (+4.5 to undead!)....

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Um. OK. Nevermind. I just now realized that EVERY CLASS that is PROFICIENT with a short sword is ALSO proficient with a LONG SWORD except the MONK...... And, in that case, the Longsword would still NOT be counted as a "monk" weapon.... So using this great, shortsword/as a longsword would NOT be practical for a Monk.... So its a moot point. (I'll leave my comment here anyhow.... Maybe someone will correct the typo in the DM Guide or something.... ha.  Or maybe someone reading this has a Monk character, or is a DM with a Monk character and wants to read my ravings on this topic.)

So it's basically a lightsaber.

How much does it cost?  treasure points? GP?  

if a character wielding a sun blade is invisible. Would the light that it emits be invisible as well? 

My gut rule is to say no. That the source of the light is, but the light itself is not.

Thoughts? 

Invisible to everything but truesight

You can work it in to your back story useing trinkets

Hmm, guess what magical weapon I gave my friend who is a Star Wars fan? It's a pretty hard question, but...

It fit perfectly into my new characters backstory.  He is a Pact of the Blade Celestial Warlock.  His pact weapon was a gift from his patron.  Guess what it was. ;)

Jeremy Crawford says not a monk weapon: https://www.sageadvice.eu/2015/10/19/can-a-sunblade-be-used-as-a-monk-weapon/

He also says, as DM, he'd probably allow a monk to use it nonetheless.

Personally I'd rule its size is determined by the wielder. So dexterity classes would use it as a shortsword (and in Monk case, at higher level you'd get to use d8/d10).

Quote from JavaPhysics >>

 2) "Proficiency with a longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it."

It's not a question of a typo, it's a question of mechanical transclusion on D&D Beyond. That text doesn't exist in the DMG. It exists in D&D Beyond because the item is templated from a generic longsword.

Thanks for the clarification!

Thanks for clarifying this. I didnt notice the template thing until you did. The text also exists in the moonblade details.

Quote from JavaPhysics >>

AND.... IT'S A BIG DEAL.... because.....while we are on that topic... It further states that "this magic longsword has the finesse property" ! Sooo..... does this imply that a character who normally only uses SHORTSWORDS with DEXTERITY (not strength) can now suddenly use this LONGSWORD as a LONGSWORD, but using their DEXTERITY for the attack, taking advantage of a longsword's 1d8 slashing damage one handed.... and 1d10 slashing damage TWO HANDED!?? And on top of that you add +2 to hit AND +2 damage? (Plus 1d8 damage on top of that to Undead!?)   THAT is GREAT for someone who normally USES a LONGSWORD (with strength) but CRAZY GREAT weapon for someone who normally CAN'T use a longsword, but only uses short sword.... Um.... Imagine taking away a dexterity-users shortsword that normally does 1d6+dex damage, and replacing it with a two-handed longsword that can do 1d10+dex+2+1d8 to undead..... You went from an average damage of 3.5 + dex.... to 7.5 + dex (+4.5 to undead!)....

 

Yeah, my rogue in a recent campaign had a sun blade, and it took me a while to realize I could use it 2-handed and get a d10 damage dice, because I was just so used to the limitation on my sneak attack capabilities, and also wanting to use my Dex instead of Str. So in the end for a rogue, it could be 1d10+Dex+2+1d8toUndead+SneakAttackDice. It was glorious, especially on a Crit.

Is it too OP to give a bunch of minions facing a LVL 4 party (2 people, I know it’s small) these blades? The minions aren’t that powerful, and bumping their +2 to hit up to a +4 wouldn’t be too OP, or atleast I don’t think. 

Hi friend!  Ultimately, you should go with what makes the most sense for your players and your setting.  

My honest advice as a DM is that this might be unbalancing.  These are Rare magic items and, if not wholly unique and one-of-a-kind, should probably be reserved for an impactful, significant event rather than be relegated to the hands of minions, unless you’re just looking for a way to hand them to your players.  
The caveat here is that the needs/fun of your campaign supersedes anything else.  Maybe these minions just ransacked a holy temple of the sun and are making good with their contraband weapons when your two heroes show up to stop them.

Thanks, that helps a lot. I’ll think about my options. I’m running the game in two weeks (I started pretty early).

It's just sort of Default Text since Sun Blade is a Longsword. So it's a shortsword that does Longsword damage.

Loving the fact that Sneak Attack with this weapons deals additional radiant damage. which is way more useful than slashing, piercing or bludgeoning damage :)

so a lightsaber