User blog comment:ObsidianLazarus/Aghanim's Scepter Theorycrafting/@comment-4012115-20140115103042/@comment-4636093-20140116150207

Dota mages scale on how many casts they can do. So yes Refresher is correct however also buying more CC from Sheepstick, Eul's Scepter, etc. also increases the amount of times you can hit the enemy before they get away.

And of course mana/mana regen.