It’s been a couple years since you played Minecraft, but hey, you bought the game. What do you wanna do first?
Let’s go down a couple Y levels.
You’ve mined below stone into deep slate at this point. It’s taken you a while, but you’re not very afraid. It’s still the same experience; you’ve been going through caves and making tunnels, but then you start to find these blue blocks. They’re really dark and look like a fungus, it must be a new update. You mine through. They drop a lot of XP. Sweet!
The entire area is shrouded in dark blue. I’d watch my step if I were you.
You take a couple careless steps forward. Nothing out of the ordinary.
You hear a sound you’ve never heard before to your left. What?
You don’t see what activated it, so you keep exploring. He’s not here yet.
You don’t hear the sound again, thankfully, and eventually get bored, take your XP and leave. You might come back later.
Congratulations! You’ve just avoided an encounter with The Warden! Presumably, if you would’ve run into it, The Warden would’ve immediately killed you and you’d lose all your stuff, but I’m here to explain how to not make that happen.
To preface, The Warden spawns in deep dark biomes, approximately anywhere below Y Level 0 and under a mountain. It has two types of attacks, ranged, and upfront. Ranged is what usually kills you.
When you are confronted with The Warden, you will notice cannot see players, only hear them, so any noise you make is to your detriment. If he does not find anything, he will start sniffing the air, and any nearby mobs, (including you,) he charges on sight.
The Warden doesn’t spawn the same way the Dragon or the Wither does. It’s invited. He spawns at the sound of four sculk shriekers, and if you’re not careful and counting for shrieks, you’re going to set it off. The sculk shriekers react to another block, sculk sensors, who vibrate if they detect noise or lots of movement, same as the Warden. Your goal is not those guys however, your goal should be the shriekers. Break them as quickly and as quietly as possible. Both blocks are going to be scattered all over the place, but they will be in range. You do not want to be loud.
By not setting off a shrieker, you should be able to get around the deep dark without much hassle.
But if you do manage to set off a shrieker four times, well.
You have 6 seconds to run.
GIF taken from GeekFlare's article: How to Defeat the Ultimate Mob in Minecraft: The Warden (no relation)