To send the hero into the mess with minimal knowledge so that you can fill in the readers along with the character, he can swear a vow or otherwise pledge himself to fight the evil that is already in possession and control of wherever the hero will have to go. Fight the evil sorcerer. Rescue the princess stolen a century ago and trapped in the heart of the evil warlock's lair. Resolve to walk off with the fabled Dragon's Heart ruby and prove he's the best thief the world ever saw. Recover the glowing opal that your fool of a father lost. Rescue the innocent and redeem your grandfather's failure to save them.
There's a lot of possible motives, and they can put the hero all over the map as to exactly how heroic he is. . . though, no doubt, every one of them will have to develop as he collides with the reality of the villain's evil. Ooo -- free character arc. And a structure for the plot, with rising tension from rising knowledge. And you get the hero's taking the initiative.
It's got stuff going for it.