D&D 5E How to surprise my players with an unexpected monster?

[SheWantstheD&D]

I have a campaign that's got a pronounced Greek mythos flavor (two of the players chose Olympian clerics independent of each other). I'm putting together an adventure around the myth of the Python of Delphi wherein the players will fight a monster at an abandoned temple. The idea is that they will scope out the site and investigate around the nearby town to determine what the monster is in advance. For reasons, I plan for the monster to be a Medusa which they can resolve without combat (read: TPK).

The problem is I'm not sure how to sufficiently surprise them with leading/misleading clues. For example, a Basilisk can also turn people to stone but what would make a player think "basilisk" before "medusa"? Or Naga with a petrification spell? Or some form of other less powerful draconic monster? I don't want to flat out lie (thought I'm sure one of the NPCs they interview could) because I feel like that would be bad DMing. What are your ideas?

 

[iserith]

If your campaign already has something of a Greek flavor, many players may assume they will run into classic monsters from Greek legend at some point, including a medusa. It doesn't seem likely you'll surprise them with a medusa as a plot twist or something. If I were you, I'd just make it a dragon (which Python is sometimes represented as) and swap out its breath for that of a gorgon. The players will see the statues or hear rumors about the creature's terrible power, likely assume it's a medusa, then actually be surprised when it's not. Give it some lair actions that speak to it being at the heart of a place of oracles - something along the lines of dice manipulation would be neat.

 

[Thurmas]

Perhaps there was a Medusa but something bigger and badder already beat the heroes to the punch. Green Dragons, for example, covet humanoid sculptures.

You could leave the medusa's head at the entrance to the lair as a warning/trap.

 

[MarkB]

If you want to surprise them, have the medusa be out on the prowl rather than in her lair, so that she finds them as they're scoping out the place.

 

[Lanliss]

If your campaign already has something of a Greek flavor, many players may assume they will run into classic monsters from Greek legend at some point, including a medusa. It doesn't seem likely you'll surprise them with a medusa as a plot twist or something. If I were you, I'd just make it a dragon (which Python is sometimes represented as) and swap out its breath for that of a gorgon. The players will see the statues or hear rumors about the creature's terrible power, likely assume it's a medusa, then actually be surprised when it's not. Give it some lair actions that speak to it being at the heart of a place of oracles - something along the lines of dice manipulation would be neat.

Man, a Dragon with Portent sounds scary. that could be two more legendary resistances, or an automatic saving throw failure for one of the players.

 

[iserith]

Man, a Dragon with Portent sounds scary. that could be two more legendary resistances, or an automatic saving throw failure for one of the players.

It could be done as something like a terrain feature - like if you take an action to breathe in the hallucinogenic fumes emanating from a crack in the ground, you get the benefits of Portent at the risk of a significant amount of poison damage and a stunned effect. That way the PCs could feasibly benefit from it as well. Make the dragon a green dragon or some variant on that so that it's immune to poison.

 

[DEFCON 1]

If by some chance you do want to keep with the medusa idea but still want to surprise your players... then my suggestion would be a medusa beholder.

A giant floating medusa head, one of its eyes put out so it now only has one... and 10 single-eyed snakes for hair, each one capable of casting the same abilities that the normal beholder eyestalks can (including petrification.)

They sure as heck wouldn't be expecting that!

 

[Corwin]

Man, a Dragon with Portent sounds scary. that could be two more legendary resistances, or an automatic saving throw failure for one of the players.

Ooo. I really like the idea of some kind of huge, powerful serpent-like creature that is plugged into the divination magic of the oracles, gaining brief glimpses of the immediate future. With something like this, maybe?:

LEGENDARY ACTIONS
The Python of Delphi gains four legendary actions at the end of each of its turns. It can use these actions at any time between then and the start of its next turn, when any unused legendary actions are lost.
The Python of Delphi can use the actions in the following ways, each of which expends a number of the actions:
2 actions—At the start or end of any creature’s turn, roll two d20s and assign one of the two results to that creature as a portent. At any time before the end of the battle, the Python of Delphi can choose to expend the portent result to replace any one d20 roll made by that same creature. A creature can have only one portent assigned to them at a time.
1 action—Make a bite attack at the start or end of another creature’s turn.
1 action—Make a constriction attack on a restrained creature at the start or end of their turn.

 

[The Crimson Binome]

It's hard to predict where the players might go, or what they might do when they get there, but they would probably be surprised if they met the medusa as a person before fighting her as a monster. Maybe she also runs the local apothecary shop, and keeps an illusion in place so that nobody suspects her, but is suspiciously well-stocked on certain poisons. Maybe she hires the party for a quest, to rid the neighborhood of mirrors, because she's had visions of a monster that can enter our world through shiny surfaces.