|DM notebook sketch|
This is an antagonist that I sort of made up, mostly stole. It's a stationary boss-preview monster.
When a wizard is tired or her message is mundane, she'll send a courier or put it on the clacks, just like us regular folks, but when a message is really important and secrecy is imperative she'll probably send it via fire.
Really, it's not that hard if you have an appropriately prepared brazier on each end and know the right semantic coordinates. A few minutes of concentration and poof, your face appears bobbing and flickering in your correspondent's flame, and their's in yours. It's a skill nearly every professional wizard knows.
Cunning wizards of particularly deft power don't even need a special preparation on the other end. They can speak or spy from any mundane fire. This has created a bustling trade in herbs and hearth additives to prevent this sort of intrusion.
|Praman Nand on Hell 71|
This is a concept that's been omnipresent in folklore and fantasy fiction but the above panel from Kill 6 Billion Demons has really stuck in my head.
When an archmage, demonlord, or other major, campaign-arc defining bad guy needs to communicate with his lieutenants, cultists or assorted party-level appropriate mooks, he can give them a call via a furnace level inferno. It'll project him super huge and scary and with a thunderous booming voice.
It makes him feel important. Better yet, it gives scrappy adventures a chance to interrupt a bad-guy teleconference and meet the Big Bad while they're still low level without getting squashed.