High-voltage power supply based on the TDKS line transformer (the Soviet analogue - TVS will also do). First of all, it is worth remembering about safety precautions, high voltage is a risk of getting an electric injury, but the high-voltage arc is also harmful due to the ozone and ultraviolet radiation emitted.
Using a high-voltage power supply, you can build many interesting and useful devices: an ozonizer / air ionizer (used for disinfection); an electric smokehouse that smokes several times faster than a regular one; you can get Electret - a material with its own electric field.
The master oscillator circuit is assembled on the basis of a multivibrator, it will be posted in the telegram channel
https://t.me/radiomansarda