The Wither Beast is an enemy from the Old One's Armyevent. When within 25 tiles of a player, it will surround itself with a 50×50-tiles aura of crystals, visually similar to the Dryad's Blessing, inflicting the Withered Armordebuff, which halves defense. The debuff will dissipate immediately after leaving the aura zone. Eventually, the Wither Beast will enter a state where it will remain stationary until it is killed. It will also regenerate its health when damaged, healing at a rate of 25 / 50 / 63 (in Tier 2) or 70 / 140 / 178 (in Tier 3) health every second.
Along with the Etherian Lightning Bug, it is one of only two enemies in the event that require the usual 50 kills to receive the respective Banner.