The Ultimate Weapon Reborn

is episode 219 of the original Naruto anime.

Synopsis
Although his comrades are defeated, Hōki puts his final plan in motion by using Gaara to revive the "ultimate weapon" of Takumi Village, Seimei. To do this, he traps Gaara in a metal sphere that starts draining his chakra. Gaara partially transforms into the One-Tailed Shukaku--which is what Hōki wanted all along.