Treevil is a walking tree enemy found in Mario & Luigi: Bowser's Inside Story. Their name is a portmanteau of "tree" and "evil". They can be encountered in Dimble Wood. It appears in two forms, one with sad glowing blue eyes and one with malicious red eyes, the latter holding an acorn on its branches; these Treevils are stronger. To attack, a Treevil throws twigs at the character. While playing as Bowser, Treevil will either lob the twig high into the air, forcing Bowser to use his shell defense, or throw it so it bounces along the ground, forcing Bowser to counter it with a punch. If a Treevil has an acorn, Bowser can inhale it using his Vacuum attack to restore 20 HP. When Mario and Luigi encounter a Treevil, it attacks in the same way, but the Bros. must counter the twigs with their hammers. The stats increasing with the berry is similar to Pidgits from the previous game.
Names in other languages