Risk of Rain 2 - The Long Road Challenge (20 Rounds)

This is the setup my friends and I used to do the twenty challenge.

Other Risk of Rain 2 Guides:

Overview

Highly recommend doing this in Co-op, having at least one engineer, and playing on drizzle.
I was playing as the engineer and the main thing to look out for are worms, especially the lightning one. The second thing to look out for are the imps that can teleport into your circle.

Required items are afterburners ( adds charges to shield). You only need one for almost 100% uptime. It helps to have another afterburner or an alien head to more easily achieve near 100% uptime of your shield.

As many mushrooms as you can get. Trade in all your items for mushrooms, have your friends trade some for mushrooms. Once you get about 20, you should be good to go but still try and get as many mushrooms as you can. Your turrets will apply the mushroom buff and provide AoE healing. The more mushrooms you have, the bigger the healing circle and HoT. It is highly recommended to give all mushrooms you find even later in the game to the engineer.

Most stages you can bypass with going straight to the boss. It is recommended to look for newt altars later on, as red items are very powerful and you can trade for them at the shop.

Recommended to have the healing antlers for all players on your team. My friend was healing for 3k+ per tick with one healing antler.

My friend highly recommends occular hud (100% crit) with mage flamethrower. It was melting bosses.

Against bosses, the main idea is to drop both turrets nearby and make sure they fit in your bubble shield. Then, just keep the bubble shield up and wait for your friends to melt the bosses.