Let's Read the 4e Monster Vault 2: Neogi
I believe the Neogi first appeared as an element of 2e’s Spelljammer setting. In 4e, they make their debut here in the MM2.
The Lore
Neogi are bizarre-looking spider-centipede people who originally hail from the Far Realm. Their culture is a particularly cruel and pitiless variety of imperialist capitalism. Ownership is all - the strong rule and own the weak. They organize themselves in clans with slavery-based internal hierarchies. A given neogi literally owns their immediate underlings and is in turn a slave to its immediate superior. This goes up all the way to the Great Old Master of the clan, who is no one’s slave. Neogi are a single-gendered species without any concept of family. All of the clan’s eggs are carried and gestated by the Great Old Master.
Neogi are renowned both as traders and slavers, following the same school of commerce made famous during Earth’s Age of “Discovery”. If the other party is weaker than you, rob and enslave them. If they’re equivalent or stronger, negotiate and trade. They just love trading with similarly unsavory people like devils, duergar, and drow. The only ones they avoid are the mind flayers, since the entire neogi people was once enslaved by entities similar to flayers back in the Far Realm.
For some reason, the MM2 doesn’t mention any of their nautical proclivities. I guess this part of the Astral Sea wasn’t quite as fixed in the authors’ minds back them. But since later descriptions would reveal you can pretty much transplant all of Spelljammer directly into the Astral Sea, you can bet you have Neogi trade/slave/warships roaming that plane.
The Numbers
Neogi are Aberrant Magical Beasts. Most are Medium, but Masters are Large. Their levels cover the first half of Paragon Tier, making them appropriate encounters for the Underdark or Astral Sea. Like all monsters, their level can be adjusted if you want to feature them earlier or later. They usually have climb speeds and darkvision, and a degree of telepathy. They also speak Common and Deep Speech.
All Neogi are immune to the Dazed condition. Their attacks are usually some sort of psychic power, though the exact effects vary per stat block.
Neogi Slaver
A relatively “typical” individual, likely found as crew in an astral vessel or as troops in raiding party. In either case, they’re likely to be accompanied by plenty of non-neogi slaves. These are some of the few monsters in the book who would make use of the “non-lethal takedown” rule, where you can decide someone you took to 0 HP is not dead, just unconscious. After all, dead slaves are worth nothing.
Slavers are Level 10 Controllers with the Leader keyword and 106 HP. They have a ground speed of 8 and a climb speed of 6 with Spider Climb. Their basic melee attack is a weak bite with an ongoing poison damage rider. The first failed save against this poison also slows the victim (save ends both).
Their main ranged attack is a Charm Bolt that targets Will. Instead of dealing damage, it inflicts a -2 penalty on any attacks that don’t include the slaver as a target (save ends). After the first failed save, the slaver also becomes invisible to the target of the bolt!
Their other attack is Psychic Shackle (Recharge 5+), a Close Blast 3 that targets Will, deals psychic damage, and dazes those it hits for a turn.
Once per encounter, they can also use Thrall Goad as a minor action. This allows all allies within 6 squares of the slaver to make a saving thrown with a +5 bonus.
Neogi Spawn Swarm
Neogi larvae are tiny and sub-sapient. Their only desire is to eat all nearby available meat, living or not. They can be dangerous in large numbers, which is what this stat block represents.
The Swarm counts as a Medium Level 10 Brute with 131 HP. They have the standard swarm resistance to melee and ranged attacks, and a vulnerability to close and area attacks. Their ground and climb speeds are both 6.
Their Swarm Attack aura (1) deals automatic poison damage, and their bites are similar to that of the neogi slaver but deal more damage. When first bloodied or when slain, the swarm lets out a collective psychic scream that attacls a close burst 1 and deals psychic damage with a Daze rider.
Neogi Great Old Master
These Large individuals rule over entire clans, and carry all of the clan’s eggs and larval broods in their immense abdomens. They’re Level 16 Controllers with 157 HP, a ground speed of 6, and a climb speed of 4.
Their basic attack is a Reach 3 Scythe Claw that damages targets and knocks them prone. Their main ranged attack is an Enslaving Bolt that targets Will, deals psychic damage and inflicts one of those progressively worsening conditions. The immediate effect is that the target gets a -2 penalty to any attacks that target the Master; after the first failed save, that worsens to a Dominate effect; and after the second the domination lasts until the target’s next extended rest. Yes, this does mean that an unlucky PC could find themselves trying to avenge the Master even after it’s been killed by the party.
When the Master is first bloodied, its abdomen ruptures and releases a Larva Burst. This works as a Close Burst 2 against Reflex that deals physical damage and creates a zone of difficult terrain that lasts until the end of the encounter. This could also be a good opportunity to introduce a Spawn Swarm to the fight if the GM is feeling sadistic.
Finally, they can use a version of the Slaver’s Psychic Shackle that deals more damage and has a wider area.