I can’t tell you the nitty gritty, but I’ve worked with RDID in the past and can probably give you a few pointers.
RFID tags themselves, or NFC (a somewhat newer version of the protocol that can store more data) both have serials unique to each tag.
One way to work with these is to keep a list of the serial numbers in your game, and when, say, a USB RFID reader (we’ll get to that) reads a tag, it sends over the serial, the game looks up which character/model that serial is associated with, and displays it accordingly.
Another option (and I believe this is what Skylanders/Nintendo Amiibo uses) is to use an NFC tag and simply wrire the name of the character in the data.
The reader reads this data, and the game matches the string to its database (or you could have simple numerical IDs, 0x01 for one character, 0x02 for another, plain old decimal in ascii, whatever floats your boat.
As for the reader, you can get boards for RFID/NFC that hook up directly to an Arduino, or raspberry pi. In the Arduinos case, you can have it talk to your PC through serial over USB, or for a Pi, just run the game on the pi and read directly from the hardware.
Prebuilt readers just act as keybaord and type out the serial, so in game you’d either have to filter keybaord input selectively, use a controller only and tread all numerical input as serials, or whatever, but what’s probably easiest is to build one off an Arduino and read from it through serial.
You’ll need to tell me more about what you’re working on for me to help with anything more specific.
I’m currently working on a system for the space that uses NFC tags to keep track of space usage, what I’ve set up is a NFC reader board, connected to an Arduino, that will output the tags serial number over a USB serial connection for processing elsewhere. This may be what you want