(I assume this is HeartGold) You get a Bellsprout! Call it Sage Hater. Obviously, this Pokemon hates all the Sages in Sprout Tower, so it must kill at least one Pokemon from every Sage in the game. The Sage at the top of the Tower is obviously the Great Sage, so you must solo that Sage. Also, you have to solo the Kimono Girls, as they seem like sage-like characters too. You cannot evolve into Weepinbell until you reach Ecruteak City, as Bellsprout hates that place with a passion because they worship Ho-Oh and Lugia there. Sages use magic, obviously, so Sage Hater cannot use any Special moves.