"lanzar(le) un hechizo sobre algo/alguien" is absolutely OK (the "le" is optional, the higher the register, the less frequent it becomes)
(but notice that it does not imply success... he might have "thrown" (lanzar) the spell and missed (or it might have been ineffective or whatever).
Other alternatives:
"ponerle un hechizo a algo/alguien" I can't say why, but it sounds horrible.
"hacerle un hechizo a algo/alguien" Same thing.
"hechizar algo/a alguien" Notice that the "a" preposition is used for people and animals in this case, but not for things. (elfs, fairies, angels, etc do count as people for this).
"embrujar algo/a alguien" Same thing: "a" for animate beings only.
All those imply success. The victim was effectively left under the effect of the spell.
If in the context of some kind of fight or battle between sorcerers, you could also use:
"tirarle un hechizo a alguien/algo" (compulsory "a" also for inanimate)
"le tiró con un hechizo a algo/alguien" (slightly different meaning: "shot at someone/something with a spell" as if the spell were some kind of ammunition or projectile) (rather informal)
Those two don't imply success, and the last one in particular leaves ample room for failure.
Embrujo and hechizo aren't the same thing. An embrujo is always bad, evil. An hechizo could be good, it could protect someone, or make him/her look better. An encantamiento is normally good (and related to "me encanta" and "encantado/a de conocerle").
Some possible translations of the sentence you proposed:
Un hechicero lanzó un embrujo sobre un monstruo; fue extremadamente exitoso. (Now the monster will be a frog until a princess kisses it)
Un brujo hechizó a un monstruo; fue muy exitoso (Now the monster is frozen, or mesmerized...)
Un hechicero embrujó a un monstruo; fue re-exitoso <--- re-exitoso is dialectal, from Argentina and Uruguay (In need of a princess again)
Un hechicero le lanzó un encantamiento a un monstruo; fue súper exitoso (Now the lizard is competing for Miss Universe, but súper, even with the tilde on the ú is still not real Spanish)
Un mago encantó a un lagarto... etc.
