The Wither is a boss in Minecraft and Ludwig's Adventure.
Ludwig sets off to destroy the 4 dangers to Minecraftia, one being the Wither. It was created by Ravenclaw and also (indirectly) by Thibo and Witherstorm.
Ludwig is knocked out after being blasted into the sky by the Wither. While he is down, Witherstorm and Thibo are attacking it rapidly. Ludwig wakes up, and Thibo and Witherstorm take out the first 2 heads, leaving Ludwig to take out the main one, killing the entire Wither. It dropped the Nether Star upon death, which Ludwig's Team used to craft a beacon.