Psychonauts of the Cosmic Overmind

There was a conversation on Tumblr, and this popped out:

Myconid psychonauts are trying to find the outer limits of consciousness in the meld, but they require the help of outside minds as variables in their prolonged experiment. Expect astral jaunts and planar travel as you plumb the depths of the cosmic Overmind.

Myconids (and the closely-related science fungoids of the unfathomable underworld) often communicate with sapients with some manner of bizarre telepathy mediated by psychoactive spores their fruiting bodies naturally produce.

Science!

(Maybe you find them in this rad Dyson Logos dungeon?)

Myconid psychonauts lair in the Dungeon of the Third Eye.

In D&D, myconids spend large portions of time in what they term "the meld," an n-dimensional psychographic conversation. As noted in the AD&D Monstrous Manual, "For the myconids, melding is entertainment, worship, and social interaction combined. The fungus men gather in a tight circle and the elder myconid release rapport and hallucinatory spores. The entire group then merges into a collective telepathic hallucination for eight hours. Myconids consider this melding to be the reason for their existence." Likewise, the fifth edition Monster Manual adds, "They use it in the pursuit of higher consciousness, collective union, and spiritual apotheosis."

By all accounts, they're intelligent and friendly, trying to hide from predators and spend their time in the meld, exploring infinity. But is a single, unified perspective truly enough to understand the cosmos?

Is this a pigeon?

Enter the player characters. They are recruited by a group of myconids attempting to understand the universal over-soul, and determining they need additional data. (Myconids aren't nearly ruthless enough to, say, dump rapport and hallucination spores in a nearby human town's water supply, which is why they have to rely on the consent of occasional passerby. Like adventurers traveling through their dungeon.) As such, they offer to allow the player characters into the meld, giving them a heavy spore dose so they will astrally project among the realms.

They probably know enough about sapients to offer payment, if nothing else.

Assuming they're all friendly myconids, of course...

It's a great excuse for some very weird plane-hopping action. You want to basically have a different genre or setting every session? Here's how you do it. You want a fantasy version of Anne's psychedelic sci-fi campaign setup? This is also how you do that.

You can justify anything in this context: a rollicking jaunt through Narcosa or a psychedelic dive into hallucinatory William Blake-esque cosmology or even a jump into other games or genres. Take your bog-standard Forgotten Realms game into the Dreamlands (perhaps even through Ultan's Door) or into Dark Sun or into Boot Hill or into Traveller or whatever.

It never got weird enough for me.

It's up to you how much you want to cleave to the setup or the logic of the setting. Do they arrive in astral form, impervious to all harm but spiritual? Does their equipment come with them? What are the parameters?

And what is the goal? Are they just reporting back to the Science Fungoids all they find, recording their experiences for posterity? Are they looking for something specific? Do you plan on them actually meeting the Cosmic Overmind and communing with it?

That's up to you.

This is your brain on myconid spores.

Edit (07-16-2019): Interested parties might wish to read the addendum to this post for some hastily-considered game mechanics.