These blocks are known as “Sculk Sensors,” a mechanism that awakens the forceful Warden. So, how do you get and use these sensors in Minecraft?

Minecraft: Java Edition is surging ahead with the upcoming 'Caves and Cliffs Update,' releasing a new snapshot that adds the dripstone biome and the sculk sensor.

Sculk Sensors also generate naturally in the biome, and these are the secret to spawning a Warden. A Minecraft Warden spawns when its 'warning level' reaches four.