Archdemon: How to deal 1B damage

Presentation

The Archdemon is found at the end of any chapter of the event
You can fight him as much as you want, but you need to restart and complete a chapter every time
The buffs you buy from the workshop also count for this fight
You get a chapter-specific damage multiplier (10% - 100%): the higher the chapter, the higher the bonus

Getting enough coins

Lose twice near the end to get more coins with the wealth talisman
Buy your heroes as late as possible, but pin cards on the way
Buy random cards and sell back those not needed. Keep temporary heroes to reach the boss

How to replicate

Use exactly the same setup as indicated: relic, heroes, colors, wealth buff (number of coins). The slightest change will ruin your try

There is a small margin of error on the wealth buff. Probably by 10's (700-709, ...). Start higher, go down by spending three at a time.

Colors matter, not levels: 1/7 and 2/7 are the same (violet). 3/7 to 6/7 are the same (orange). Exact same power level.

The chapter does not matter: it only provides an end bonus

See advices above to get enough coins