With radio, they could cause electrons in their local vicinity to vibrate at specific frequencies which would generate radio waves. These waves would then span the distance between the two communicators at the speed of light. They could even manipulate the waves themselves to be sure they are moving in the right direction. So it would work just like a radio:

1) The messenger manipulates the electrons which causes the wave. He then directs the waves to travel to a specific region.

2) The waves travel at the speed of light to their destination.

3) The receiver detects the waves and manipulates electrons in his area to decode the message.

Maybe using the whole quantum entanglement idea.
https://en.m.wikipedia.org/wiki/Quantum_entanglement?wprov=sfla1
I think this would work with your rules of being able to sense and manipulate energy

They could have a system of manipulating the energy locally that would then immediately have an effect on the energy in another location. It's a loose interpretation of the principle, but seems close enough

I am going to steal Eth's comment to eternalize it as an answer:

Via earthquakes, of course! – Eth

This works regardless of the time setting. Medieval people would never understand radio but Earthquakes would be something really concrete to them. They could then develop some sort of wizard morse code, or better yet, use earth or stone golems as modems.

Some advantages of using this method:

• Signals travel 2 to 8 km/s on the crust, and up to 13 km/s in the mantle. They also follow straight lines to the destination. That is not only faster than a messenger on a horse or mail pidgeon - it is faster than sound in air!




• Very good signal-to-noise ratio (except for those living in the Andes);




• Omnidirectional, so perfect for broadcasts and group chat;




• Can be modulated and filtered by amplitude or frequency to allow for different channels, so that quake conversations don't interfere with each other;




• Can double as a weapon if you don't like the recipient.

For anyone thinking this is a joke answer: seismic activity doesn't have to be something that shatters the Earth and damages buildings. Most seismic activity in the world is so weak we don't feel it. And the OP said at the start of the question:

Sorcerers possess the ability to sense (...) energy;

Toph and the republic era earthbenders from Nocklodeon's Avatar come to mind, with their seismic sense.

By using the Pen of Flame

Sorcerer A and Sorcerer B wish to communicate at a distance.

• "A" conjures a flaming pen.


• "B" senses that a flaming pen (as he has the ability to sense energy created by sorcerers).


• "B" then creates a flaming pen of his own which "A" senses.


• They each place the pen on a nearby scorchable surface


• They exchange control over their flaming pens so that the other sorcerer can burn messages into being.

There are probably similar and simpler ways for them to do this, but if you're a sorcerer and can use a flaming writing instrument, why wouldn't you?

Depending on how much you care about being overheard and how much of an issue efficiency is, you could use something akin to Morse code or tap code... with lightning strikes or something of equivalent brightness. Since this is the Worldbuilding SE, the fact that this would be literally awesome can't be ignored.

Quick search says that your average lightning bolt is five miles high... some quick math says you're going to get about 400 miles.

A wireless telegraph

Each sorcerer has a special box or slate they've created made of materials they can manipulate in color or light. Just very simple, like early telegraphs.

Now they can spell out messages in Morse Code. This code was not yet invented in Medieval times, but solely because there was no need for it. It would not be difficult to come up with a concise system for communicating digits. Morse Code uses 3 states: long, short, and off. That's all you need.

A servant on the receiving end could transcribe the incoming message. With the right buttons and levers, a servant on the sending end might be able to transmit the message, if the magic can work that way (if the sorcerer doesn't have to stand there and will each mode change into being).

A wireless teletype

A more sophisticated version could show letters on the receiving end. Single words, like a teletype, would be even better.

I'm imaging something like a Liquid Crystal Sheet only one made from materials available in the era and that uses manipulations of heat from below the glass to form letters. Glass was available in Medieval times, though it was expensive and not the same quality we are used to. But some magic may help in making clear flat sheets (about the size of a tablet).

Or perhaps an Etch A Sketch

If the sorcerers can finesse small lines that stay until the entire thing is reset, they could communicate some pretty complex messages. Etch A Sketch was a common children's toy back in my day. It uses a glass screen and aluminum powder. No electricity. You "reset" it by shaking the screen.

If your sorcerers can manipulate magnetic energy (and use iron powder), this could work.