Grim Idle

A ritual is essentially a character reset. You can go all the way to Zone 10 naturally (pop that achievement and others along the way) and then do the "reset" as this is the best path to a quick completion.

To perform the Ritual, you will also need 10 candles so it's not available until you have killed the first few champions anyway (enemies with a star above their head who drop them upon death). After the first one (going to Zone 10), you can now just get yourself to 10 candles on the subsequent 4 runs.

You need to use to to access the in game menu. Go to the ritual section and choose to perform one. You will reset back to Zone 1.