Mini Module: Primordial Peninsula

The players wash up on a mysterious island full of dinosaurs and dire animals, then begin to transform into similar creatures.

Catch a Ride

The party can find themselves in a fishing town, contracted by some of the families there that have had their loved ones disappear while out sailing. Or they could be traveling somewhere else and need to take a ship across the ocean. They might also be enticed by tale of treasure on a nearby island. Either way, they'll need to end up on a boat.

Wild Waves

As their boat nears the island a violent storm picks up. The players will need to make DC 15 Acrobatics checks to avoid being thrown from the vessel.

The weather rapidly begins to change for the worse. Stormy clouds and high winds blow in, causing large ocean swells that crash against the boat. A heavy rain starts to fall, making it difficult to hold on as your ship sways in the violent waters.

The island will come closer into view, only for the boat to crash against the rocks. The players will need to swim for the shore, or be washed up on it. Their boat will be completely destroyed, leaving them stranded.

The Party Changes

As the island is explored it's discovered that it's full of dinosaurs, near-humanoids, and dire animals. Additionally as they explore they begin to develop helpful minor mutations, bigger legs to jump higher, claws to climb trees, wings under their arms to glide, etc. These can be useful for getting their bearings on the island and navigate up cliffs or trees. If they have any mounts, animal companions, or familiars those will also begin to transform similarly.

The party will need to use their helpful transformations to overcome some obstacles, only to find themselves transforming even further and becoming more animal-like. The types of creatures they transform into are just like the other creatures on the island: dinosaurs and other prehistoric dire animals. Their attributes can change, but their skills and abilities will remain. Some may not be able to hold their weapons anymore but will grow claws, powerful tails, and other parts that will allow them to attack with the same attack and damage of their previous weapon, but without any magical modifiers.

This can also be a good opportunity to switch up attack types and roles. Have the wizard grow strong plating on their back and tail. The barbarian could become a wiry animal with wings that shoots spines from range. Long claws for climbing and burrowing could make a more mole-like animal. Some time before the session you could strike up conversation about everyone's favorite dinosaur and have them turn into those.

Have a small encounter with a dinosaur or two from page 79 of the Monster Manual and let the players make use of their transformations to defeat, avoid, or otherwise overcome the dinosaurs. Afterwards, they'll transform further.

A Friendly Community

The party, now fully transformed into prehistoric animals, comes across a large nest of other prehistoric animals. Now that they've transformed, the players find out the creatures are friendly and can be understood. Many don't recall much of their past, but some have vague recollections of dreams they've had where they once walked around on two legs and called themselves elves, dwarves, humans, etc.

The animals here are friendly and immediately welcome the players, saying other animals just show up now and then and join their community. They hunt and play together and seem overall happy with their lives here. The players will be asked their names only to realize they've forgotten them. The other inhabitants will encourage them to come up with new names. If confronted about their pasts and supposed former lives the inhabitants have no actual memories and will firmly believe they were born and grew up on this island with the other animals. There are no sinister characters or other things to suggest that anyone in the village is responsible for what's happened.

Further Exploration

After becoming acquainted with everyone and the nest, and maybe becoming a bit comfortable, the party is sent to gather food from in the forest. Or if the players reject the nest and leave they'll re-enter the forest. While foraging/exploring they find notes, journals, and stone carvings deeper in-land from the shore towards the middle of the island. They describe expedition parties and stranded people that washed on the shore and experienced a similar transformation to the player's experience.

Day 1, 7:00 am
We have reached the island and begun our expedition.
Day 1, 9:28 am
Remarkable! Dinosaurs and other ancient creatures reside here.
Day 1, 10:02 am
Some of the lads have developed rashes, must be cautious of plants.
Day 1, 10:14 am
Not rashes, mutations. Growing tails and hooves. Getting hard to write.
Dy 1 1111
Help

One wizard's tome says that there's a powerful magic emanating from the island's active volcano with the last entry deciding to go check it out.

Stranded, spell gone wrong. Not sure where this is, I might explore a bit before returning.
I've started to develop changes, my spell went more wrong than I thought. I'll need to rest and re-memorize before I teleport back to my tower. Perhaps I can find reagents here to investigate my changes.
More changes. Harder to focus on spells. There's strong magic coming from the volcano, could it be involved? Going there now.

Others are more frantic and fearful, worrying about what they're becoming and wanting to go back to their former lives.

Someone please help. My body is beginning to change, mutating. I don't want to change. I want my to go home. I want to see my family. I don't want it I don't want it I don't want it I don't want it I don't want it I don't want it I don't want it

They can find more clues and similar journals until they should ultimately decide to investigate the volcano.

The Volcano

After a few hours of making their way through the forest they'll emerge from the trees.

The tree line gives way to a large plateau of obsidian. The active volcano is in the middle, billowing smoke and oozing lava into the sheer rock valley below.

As the party approaches it has a small eruption, sending out ash and brimstone which the PCs need to dodge or take 10 fire damage. As they start to scale it they'll quickly find a large cave opening, cleanly carved like a doorway. Inside is an open floor plan among rivers of lava. A small wizard's workshop is set up, with a large glowing crystal at the center of the room. Upon entering the room, 3 golem defenders will activate and attack.

The golem listed here is suitable for a party of level 3, but you can use any level-appropriate encounter and reskin the monsters to be golems. Try using the encounter generator here: https://www.kassoon.com/dnd/5e/generate-encounter/ to make your own.

Encounter

Map

(Credit to UrzasMine)

The crystal must be shattered by any means. Attacking it will create large cracks, and enough attacks will shatter it. If the players immediately start attacking it instead of the golems its HP and AC is equal to a golem (HP 42, AC 14 if using golem above). If they deal with it after combat then just have a few hits break it instead of requiring attack rolls. In this combat the party should be encouraged to make clever use of their new forms. You should generally allow any plan that makes use of their new powers to work.

The Players Change

Upon shattering the crystal the players return back to their original form, along with the other humanoids on the island. Everyone will suddenly remember who they are, and their lives from before.

If they explore the workshop they'll find scattered humanoid bones, as well as journals from the wizard that lived here.

Work continues on my experiments. I have relocated this lab to a remote island so that my work won't be discovered and misused. I have made good progress on reversing the disease, and my assistant is hopeful we'll be able to cure my beautiful Julia. I wish I had his optimism.

A misfire for sure. Experiment 87 was tested today on the crystal, which turned my assistant into a snarling beast. I was able to contain him, but I've created some golems to better handle any future mishaps.

It's proving difficult to return my assistant to normal, it is possible that Experiment 87 has contaminated the crystal in some way. I will perform more tests with my assistant and the crystal tomorrow.

Everyone will gather back together at the nest, including the wizard from the second journal entry on the island who will open a portal for everyone to return home before warping away. Once back at town they'll be rewarded by the families of the people they rescued. You can use individual, hoard, or maybe just part of a hoard appropriate to your party's level at https://www.kassoon.com/dnd/5e/treasure-generator/. For level 3 players you may want to give them about 1000 gp or so.

On each of the players some small remnant of the transformation should remain. A small patch of plating on their back, slightly sharper teeth, and other minor cosmetic changes to remind them of their time on the island.

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