16gt wither killer

DO NOT USE THIS DESIGN if you are not sure redstone mechanic is vanilla or not on your server. since the layout isn't resilient to skipping tick and wither can break out Require 1 layer of 3x3 bedrock and a single air block above it. (made a mistake in box unloader, updated at july 31) From version 1.11.1 to 1.15.2, piston will push further than its piston base, causing wither eye height poping out bedrock layer, while it still mostly works, initial explosion will not be covered. Thanks for Scorpio pointing out not using the center of exit portal.