Minecraft wiki entry for How_to_get_rid_of_a_rogue_wither, associated text: Note that all of these items are very useful in fighting a wither normally. Taking on a rogue wither is significantly more dangerous, as you may have already been killed once and the wither you attempted to destroy is now running loose in an area potentially made highly dangerous. Withers can fly and will attack any living mob or player with their explosive skulls, and also heal over time, so take extra precaution when approaching. Expect to see it flying, bombarding living animals with its skulls, and surrounded by massive craters stretching deep into the stone, possibly freeing water and/or lava sources. It may be a surprisingly long way from where it originally broke free, so watch for its healthbar.