Potentially weird things you can do with a cranium rat companion

[Colbymunro]

Volo's Guide introduced a couple of new potential companions such as the Dimetrodon and Velociraptor but I think there's one that flew totally under the radar because of a potentially weird exploit I've been thinking about for the past few days. This little guy is the Cranium Rat, and while most CR 0 creatures don't make particularly good animal companions for the beastmaster I think it's potential as a scout is amazing. For one thing it has telepathy and an intelligence of 4 which means it should be capable of expressing general information (albiet primitive information) about what's in the next couple of rooms without the use of spells. If you use the revised ranger, you can increase it's intelligence enough by 8th level that it can read (and maybe even write) as well as giving it proficiency in some skills like investigation which is super weird but kind of fun.

So here's where it gets really interesting. There's really no reason your character can't have pets that aren't animal companions, even if they aren't a beastmaster ranger. After all that's what animal handling is for other than the occasional use to get a horse to go where you want it or calm a mean dog. So let's say you spend your time to start breeding and raising a contingent of cranium rats. If you are operating with the assumption that inbreeding works similar to how it does in real life you only need 2 breeding pairs (for a total of 4 rats) to get started. In real life, litters of rats are about 10-12 and they reach sexual maturity in 6 months (although males are technically capable of breeding by 6 weeks).


If enough cranium rats come together to form a swarm, they merge their minds into a single intelligence with theaccumulated memories of all the swarm's constituents. The rats become smarter as a result, and they retain their heightened intelligence for as long as the swarm persists. The swarm also awakens latent psionic abilities implanted within each cranium rat by its mind flayer creators, bestowing upon the swarm psionic powers similar to spells

That's right, you could potentially build your own swarm of cranium rats, install your companion as the leading mind of it and have your very own CR 5 psionically spellcasting animal companion, complete with 15 intelligence and 14 charisma. It takes the Cranium Rat from a weird subpar choice to potentially the most powerful, (and extremely interesting) animal companion choices in the game.

Theres a little more you can do with it because of the following wording:


a rat separated from the swarm becomes an ordinary cranium rat with an Intelligence of 15. It loses 1 point of Intelligence each day that it remains separated from the swarm. Its Intelligence can't drop below 4 and becomes 15 again if'it rejoins the swarm or another one.

You can seperate your swarm into indivuals and now have a very intelligent solitary companion for a few days. Maybe you set up a network of individual cranium rats installed at 30 ft. intervals and have them pass short range messages back and forth between your party members. Because they can activate a glowing effect which works in a 5ft radius you could do something similar to dancing lights with them (or more humorously, have them organize themselves into one of those scrolling word billboards) . I'm sure if you are creative there's a lot more you could do with your squad of very smart rat friends.

I'm super interested in knowing if any DM's out there would let one of their players do this, and if so how they would handle the rules and roleplaying aspects of it (maybe a contingent of the cranium rats get displeased with your leadership and lead a civil war, or maybe an encounter with an Illithid has negative adverse effect upon the swarm). I think there's a lot ripe for storytelling and I'd let one of my players do this if they were willing to put in the work of breeding them. I'm aware none of this is really RAW even though it's all built on stuff right out of an officially published WotC book.

[Luccan]

So, I've wanted to play a low-int Orc wizard for awhile now, just for fun. A game where no one was concerned with it, of course, so the fun would be for everyone. Now I want him to have a pet Cranium Rat Swarm. They're smarter than him, but they like him so much (and I'd pump his wisdom for the Handle Animal) that they stick around. Other Swarms joke about the pet Orc, but much like some people with their cats, it's a little unclear who is whose pet.

[Colbymunro]

So, I've wanted to play a low-int Orc wizard for awhile now, just for fun. A game where no one was concerned with it, of course, so the fun would be for everyone. Now I want him to have a pet Cranium Rat Swarm. They're smarter than him, but they like him so much (and I'd pump his wisdom for the Handle Animal) that they stick around. Other Swarms joke about the pet Orc, but much like some people with their cats, it's a little unclear who is whose pet.

I think that would be really fun! Back when I played pathfinder I had a very low int hunter with the Courtly Hunter archetype (they get to treat their animal companion's intelligence similarly to a wizard's familiar which increases as they level ) and a T-Rex companion. Playing a character with a much lower intelligence than their companion is very silly, but rewarding as well. To date it's my favorite build I've ever played.

[Falcon X]

I DEFINITELY would allow this with cranium rats. Why? Because it creates its own, beautiful plot arc.

In prior editions it was hinted at, and in 5e I believe it was canonized, that Cranium Rats are spies for Ilsensene the Mind Flayer goddess.
I assure you that there is a creative way to transition this into some kind of Mind Flayer arc of the player’s own creation.
Just, try to do it in a way that doesn’t feel like you are just cruelly taking away their toys.

In my game, I downplayed the Ilsensene route a bit.
I had a wizard on Shadowfell who was doing experiments to re-create Cranium Rats that we’re not under Ilsensene’s supervision.
He turned normal rats into Cranium Rats that could assert control over other rats, creating a giant involuntary hive mind that even could control were-rats (which were a thing in my game).
Luckily, one of he players already owned an intelligent rat. He had the wizard turn it into a super Cranium rat, then use its new powers to seize control of the growing hive, then set them all free.

[EvilAnagram]

I DEFINITELY would allow this with cranium rats. Why? Because it creates its own, beautiful plot arc.

In prior editions it was hinted at, and in 5e I believe it was canonized, that Cranium Rats are spies for Ilsensene the Mind Flayer goddess.
I assure you that there is a creative way to transition this into some kind of Mind Flayer arc of the player’s own creation.
Just, try to do it in a way that doesn’t feel like you are just cruelly taking away their toys.

In my game, I downplayed the Ilsensene route a bit.
I had a wizard on Shadowfell who was doing experiments to re-create Cranium Rats that we’re not under Ilsensene’s supervision.
He turned normal rats into Cranium Rats that could assert control over other rats, creating a giant involuntary hive mind that even could control were-rats (which were a thing in my game).
Luckily, one of he players already owned an intelligent rat. He had the wizard turn it into a super Cranium rat, then use its new powers to seize control of the growing hive, then set them all free.

I believe in Volo's Guide they have nothing to do with goddesses. The mindflayers do not worship anything, and Ilsensene does not exist. The cranium rats are direct servants of mindflayers.

[Colbymunro]

Ooh that's super interesting. I was considering this more from a player's perspective ( though if i was the DM and a player came to me I'd definitely let them do it) and I was considering playing a Githzerai who was taught the philosophy of using your opponents weapons against themselves. I think he/she would actually love and care for these creatures so it will simultaneously break my and my characters heart if they turn against them.

[bc56]

I believe in Volo's Guide they have nothing to do with goddesses. The mindflayers do not worship anything, and Ilsensene does not exist. The cranium rats are direct servants of mindflayers.

Actually, in Volo's it says that illsensine is mistaken for a god by mortal philosophers, but it is actually the state of psychic union with universal knowledge, whatever that means.

[Falcon X]

Ah, alas, the version differences.

The way I see it, all sourcebooks are just hearsay. One editions book was written by one scholar’s view of the universe, and another editions is written by a different scholar.
Me? I still follow the line of thinking that Mind Flayers are not a true hive mind Ilsensene exists.

Am I wrong?
Probably.
Fight me. I like the old Mind Flayers better.

To the OP: Go get a copy of the 2nd edition Illithiad. It’s on DMsGuild. Adds tons of mind Flayer goodness. Bruce Cordell beats Volvo any day.
3.5s Lords of Madness comes in a close second.

[Colbymunro]

Sorry to necropost but this subject started bouncing around in my head again recently. More specifically I've started thinking about mixing this animal companion with a Circle of the Shepherd Druid for two main reasons: Conjure Animal and Wild Shape. I really want to make a beastmaster ranger / circle of the Shepard druid who has a cranium rat animal companion, wild shapes almost exclusively into a cranium rat and uses conjure animals to summon cranium rat

I'm curious to a few questions on the topic of this subject, and how other DM's would house rule such a thing:
1.) How many creatures (let's use rats, because that's really what im asking about) make up a swarm?
2. ) Could you use conjured animals to breed with normal animals?
3. ) If you Wild Shaped to be part of the cranium rat swarm, would you gain control of it? Would the swarm benefit from your mental ability scores?

On question one, there doesn't seem to be any information on this in 5e, unlike prior editions. In pathfinder 1, a swarm of tiny creatures is about 300 discrete animals, but if you get into the math of hitpoints per creature corresponding to the swarm, obviously that doesn't really hold up and the swarm is more of an gameified abstraction. However, swarms in pathfinder are also stronger because of the traits they get, so I think it's fair to say a swarm of cranium rats in 5e is approximately 20 or so creatures because of the number of hitpoints it has.

As for question two... well I can see it both ways, but saying that it is possible is WAY MORE INTERESTING in my opinion. Conjure Animals summons fey spirits which take the form of animals, and they are treated as both fey and beast for the duration of the spell. In mythology there's a number of times when gods take the form of animals and breed with them, creating some really weird creatures. Personally I love the idea of a groom who is a druid who goes around conjuring studs to breed horses with the unearthly speed of the feywild for nobility who can pay top dollar for these services. Better yet, how cool is a druid who that is using artificial selection to blend the material realm's less intelligent/magical animals with the power of the feywild because theyre convinced it's the only way to really protect the natural world from the incroachment of civilization. Still though, lorewise they're spirits, so it would be totally fair of any given DM to say "Nope that doesn't work and you're weird for trying it."

For question three, well, theres issues of power balance for sure. Gaining access to Dominate Monster once a day is really good, and only improved by the fact that you could get an eighth level spell so early. Being able to improve the DC save by bumping it with your intelligence would only make it better.

TL;DR this is something I want to do with a character at some point. I think its a unique way to bring in a creature that is generally kind of overlooked by players and dungeon masters alike and raises some unique questions into the nature of the world's creatures.

[Kadesh]

1.) How many creatures (let's use rats, because that's really what im asking about) make up a swarm?
- Can you summon a swarm specifically? If no, then more than you can summon at once. It is an arbitrarily high figure. If you're going to use Simulacrum or other arbitrarily high number breaking combination, you can leave the table.

2. ) Could you use conjured animals to breed with normal animals?
- no

3. ) If you Wild Shaped to be part of the cranium rat swarm, would you gain control of it? Would the swarm benefit from your mental ability scores?
- no

[Colbymunro]

1.) How many creatures (let's use rats, because that's really what im asking about) make up a swarm?
- Can you summon a swarm specifically? If no, then more than you can summon at once. It is an arbitrarily high figure. If you're going to use Simulacrum or other arbitrarily high number breaking combination, you can leave the table.

2. ) Could you use conjured animals to breed with normal animals?
- no

3. ) If you Wild Shaped to be part of the cranium rat swarm, would you gain control of it? Would the swarm benefit from your mental ability scores?
- no

I'd like to understand your thinking a little bit more than just flat yes or no answers, but I'm gonna hazard a guess and say it's for a general sense of game balance.

One thing I didn't mention about my thinking for question three is that cranium rat swarms are a hiveminded collective that gain intelligence as they form a swarm, which is why my thinking trended towards "yes, you could assert yourself as the leading personality of it" Although I think it could be balanced somewhat by some sort of intelligence or charisma contest to become that dominating personality.