The Unfathomable Professor Mesmerismo was the first to discover the somewhat unusual properties of burning fuels other than the standard quicklime in a magic lantern. Other mineral compounds would open windows onto one of any number of other planes. Most were infernal – not a surprise considering the revolting stench of the resulting fumes – but certain incense blends revealed more benign afterlives.
The windows were hard to use as a method of communication, since the moving images had no accompanying sound. Those in the lantern image could hold up written messages to the viewer, but they had to be prompted to do so by some other means since all they saw of the magic lantern was a small globe of flickering light hanging in the air.
One operator is said to have discovered a blend of solvents & lubricant oils that would cause a lantern to show a view of Mechanus, but no one has been able to confirm whether it actually works since the exhaust from the lamp is so toxic everyone in the darkroom was poisoned dead within minutes.