Weird Insight is such a cool move, but I wonder how you'd use it when a Nothic is alone. What kind of secret could they use against a party?

Depends how much freedom you give it to be an NPC.  They are fairly intelligent, as cursed monsters go, and if they learned something useful they could use it for blackmail purposes. More useful in a political intrigue setting, or one where the person has a major secret they're keeping from the party.  Or they could just hide from the party, let them pass, maybe have them roll their saves in the next room if your players are prone to acting on meta.

Why isn't this a race? I will make one. But i can't post it on here since i'm not paying for membership. It might just be a group thing. But either way, a good way of determining what the bonus stats are is to see the highest stat for the monster/beast/animal and use them. Be careful not to make them overpowered.

@vlad, definitely not useful if one Nothic is fighting a party, but it's certainly a tasty ability for anyone who can summon or otherwise control one of these buggers. Imagine if the BBEG has a pet Nothic that they use to blackmail their foes...

My party found one of these things in a cave, gave it some food, and it left us alone.

We named it Toxic and we came back to visit and give him food as much as possible.   :D

I would use Weird Insight in RP. The Nothic knows what the party is after, and about their past. Maybe the BBEG employs an army of Nothics to work the secrets out of their enemies. 

Something bad happened to Mike Wazowski

Vax... You killed an NPC

If memory serves, these are related to Allips in that they are created by knowing too much.

These are great to inspire party role playing as well. A nothic can glean the secrets from one and share them to other PC.

Paladin to Rogue: "This nothic here says you stole my holy relic?!"

the first time I encountered tis thing I shit my pants

My druid befriended it by feeding our enemies to it lmao and now hes a part of the group and he wears a cape. 

Idea! Nothic, whose madness and nothic-hood stem from a sentient magic item it discovered. It was slowly driven closer and closer to under total control of the item, until it metamorphosed. Now, since extensive time has passed, it has broken the will of the item  using Weird Insight. An insane monster with an insane item under its control.

Quote from ClericalKenku >>

Idea! Nothic, whose madness and nothic-hood stem from a sentient magic item it discovered. It was slowly driven closer and closer to under total control of the item, until it metamorphosed. Now, since extensive time has passed, it has broken the will of the item  using Weird Insight. An insane monster with an insane item under its control.

Golem, but he broke the Ring,

does the nothic choose what it wants to learn about its target with weird insight? or is it just a random fact like "this adventurer is a cat person" or "this adventurer can play piano"

Can we please get an in-depth expansion of this super-weird creature, along the lines of the excellent entries in Volo's Guide to Monsters? Questions worth addressing: Since they can't understand the memories of their past lives, I would assume many of them can't remember their names from life. So, what sorts of names do they use? If they don't use names for themselves, what names do other intelligent creatures call them by? The fact that they have an ability dedicated to learning the secrets of other creatures, which suggests that they crave not only arcane knowledge, but intimate personal knowledge as well. And yet they are "content to watch" most of the time, which implies that they are quite solitary. There's an interesting tension here between desiring information gleaned (normally) from social interaction but also shunning such interaction. What is behind this tension? Why did Vecna leave this curse, if he himself is (or was) a lich, which means he too devoted his life to unearthing arcane secrets?

It feels like there's so much under the surface! I crave more! Give me all of your secrets!!!

I thought this was an Underdark monster, but I was making an encounter with one, and it didn't appear in the Underdark monsters section.

I would all it up just a little in one stat: give the nothic a deception +5.  While encountering a party it could roll "weird insight" but is really rolling deception and tells the wizard that the rogue took his precious gem and does discord.  This would also make them much more interesting spies.

Got to guest RP this as an NPC for my buddy running the Lost Mines. What a treat, such a great character and super fun to RP. "Always hungry never full, always watching never done! HAHAHA!!!"

Just met one I became it's friend 😁 I fed it 3 bodies I was very lucky and very close to death