Vtyjkyuk

So, their is an ancient species I’m creating, and their names are simply “The Progenitors”. They existed over 3 million years ago, I’m the Milky Way Galaxy, but sometime 1 million years ago, the entire species left our dimension, and went to on to never be seen again. The progenitors often experimented with the genes of lesser species in their time. Whenever they saw a species that had the seemingly perfect attributes for intelligent, the Progenitors gave them a little boost in IQ, and most intelligent creatures in the Universe today were created by them.

They also created some creatures for a purpose, like the Tayan. The Tayan is a biological torture species, that slowly, slowly digests it victims painfully and agonizingly. The Tayans before the genetic revamp were just slightly large pitcher plant like things with leafy tentacles.

It would be easier to just use a torturing machine, so my question is, why would the Progenitors crest a biological torture species?

Let's assume the Progenitors wanted their creations to last. Maybe not for 1 million years, but at least for millennia.

It's pretty hard to create a machine that will keep functioning for 5000 years. And probably even harder to create an automated factory that will keep creating those machines for 5000 years. We have a hard time building non-automated fab plants that last for decades. Sure, the Progenitors will probably be better at it than us, but it still probably won't be a trivial problem.

On the other hand, lots of biological species survive for far, far longer than 5000 years—in fact, far, far longer than 1 million years.

And that's just the ones that evolve naturally; if you're genetically designing them, you could do even better.

Of course eventually the Tayan will go extinct or adapt so much that they're no longer fit to purpose as torture machines. But it's easily plausible that could be way beyond the timescale of your story. (Or it could be something that happens in your story.)

Because all the technology of the progenitors is biological.

They do not build machines. All their devices are highly specialized, engineered life forms. If they need a torture device, they would genetically engineer yet another lifeform for this purpose.

The plant is designed to exploit a primal fear of one specific species.

There was some species which for some reason had a very strong community preservation drive, no personal self-preservation drive, no sense of pain and no fear of anything except being digested by plants. Let's call them "the fearless".

There might be some evolutionary reason for this. In order to create a fearless species, you could design a species which procreates once and very early in their life. Before they procreate, they are barely sentient. After they had children, they develop intelligence. Now their only purpose is to protect their children. They are willing to sacrifice themselves without second thought. When there is no danger for their children and they notice they just consume resources, they will just commit suicide without giving it second thougths.

Carnivorous plants could have been the only predators in their ecosystem. But dying to a plant caused more plants to grow. So losing too many people to carnivorous plants was the only real threat for the Fearless society, as it would have created a self-propelling feedback loop. Dying to a carnivorous plant means a sacrifice with a negative value for the community. So this is the only kind of death they fear. It is a primal fear which overrides any rational logic in their mind.

When the Fearless developed technology, they eradicated all carnivorous plants on their planet, so there was nothing left for them to fear.

The progenitors needed to extract some information from the Fearless. Divulging that information would have been bad for their children, so the Fearless would stoically endure any physical or psychological torture. Their neurology was also incomprehensible for the progenitors mind reading devices.

So the progenitors created the Tayan. And the Fearless talked.

Because you can think of any species as a 'perfect' machine. Take humans for example, is often said that we are a very complex machine with lots of different processes working at the same time to make us what we are (our circulatory, digestive, immune, lymphatic, muscular, nervous... systems; our conscience, self awareness...). So creating a species could be seen as creating a machine, only in a different way.

Also because it would be like an experiment, letting the concept of 'torture' grow and develop by its own. Because often nature and evolution work together to create very specific perfect mechanisms, and so will happen with 'torture', it would find its way to be naturally perfect.

Maybe it's more of a religious ritual. The Progenitors might need something with specific properties, like the ability to create a certain kind of acid. Machines aren't great at harvesting resources and making stuff at the same time. For example, nuclear power plants don't harvest and process their own uranium without people helping. Maybe the Tayan would require less work than a machine. An added bonus is if you need another torture device, why build another machine when you can plant a seed and wait for it to grow?

Because they harvest "pain"

The progenitors know a lot of species that produce a special set of biochemicals similar to adrenaline and adenosine triphosphate, called P41-N. The Progeitors direly need P41-N because it helped them survive for the last 3 million years.

They use torturers because artificially replicating P41-N is very inefficient. Creatures on the other hand, can naturally produce them. The problem is that these creatures only produce P41-N when they are experiencing physical trauma.

The obvious solution is to automate the induction of physical trauma on such creatures, and what better way to do so other than to repurpose entire creatures for the sake of torturing others.

Testing

They are interested in the intelligence of a species. Most of the time torture doesn't really present any options for bettering your situation, but struggling is an emotional/instinctive response. Using torture could be a quick way to test how much the actions of the specimen is driven by instinct/emotion vs rational thought.

Because a torture device would need to be maintained and a Tayan is nothing more than a biological self-maintaining self-replicating torture machine that uses semi-randomness of victims falling into kill.

That randomness could also be key here. For whatever reason they dont want to torture everyone (or they would have left something for that behind), but leave it up to chance who falls in and gets tortured.