The program you probably want to use is called Inform. http://inform7.com/

It features a natural language code structure and easily builds verb and noun pairings that allow for an amazingly complex, but easily maintained database of objects. Your creatures could be acted upon by a variety of objects in a variety of ways, for example. Of course, you can do straight forward RPG type stuff with it too.

Twine is great, but an RPG of any complexity would require you to code everything in raw HTML/JavaScript and then you'd be left wondering why you're using Twine at all.

Keep in mind that most text-based engines are geared towards "interactive fiction" (IF), and Inform is no different. If your web programming skills aren't strong, then Inform is something to try. Otherwise, I'd recommend just building a text-based RPG entirely in HTML/JavaScript. If your goal is for a standalone application (mobile/desktop), NW.js or Electron will run your web-based RPG through a Chromium browser window and let you read and write from the hard-drive, and the player wouldn't know they launched a web browser.

Good luck, Pepsidog!

What about existing MUD, MUSH, and similar engines?  Getting things converted into hyperlinks may be some work, but they have a full suite of text-based RPG systems in place.

Would articy:draft help you out? https://www.nevigo.com/

It is quite powerful when it comes to setting up conversations and other branching logic. It has a simulation mode which allows you to run the logic right there in the program and they ready-to-use integrations with unity and UE4. AFAIK (I haven't used the premade integrations myself) you can just drop an articy player into a unity scene and play the logic there without having to do much of anything on the unity side.

31 minutes ago, Pepsidog said:

I cant find any information aside from what MUD is.

MUD and MUSH engines were popular in the 1980s and 1990s.  They were the MMO's of their day, text-based multiplayer games.  The vast majority were hack-and-slash style RPGs, but there are also PvP, social/chat games, fantasy role playing, sci-fi role playing, and even educational game systems.

Some were sequential turn based, others supported hundreds of concurrent players. Most were limited by bandwidth which was generally measured in bits per second or kilobits per second.  All the popular MMOs of today can trace their roots and inspirations from the MUD and MUSH games.

Wikipedia has a nice list of major MUDs, many have links to their source code repositories. Many were written primarily in C, although you'll find some C++ a few have been updated to modern language standards. A few ports and refreshes like this one have been updated to support all the modern inconveniences like NoSQL, HTML5, JavaScript graphical clients, and Heroku cloud support, if you want all that in your text based game.

4 hours ago, Pepsidog said:

I’m not sure I want to pay monthly for that.  Is there any other options?

You don't have to pay monthly. The single-user version has a perpetual license, and of course there is a trial.

But yeah, it is not free, if that is what you are after.