What spell(s) should I base this off of?

I need a spell that when cast, makes target invunerable for X seconds and and sets transparency to 50% (that can be done by triggers), but also needs to lower the units attack damage to 0 or just disable attacking. Basicly: "Target deals no combat damage, and prevent all combat damage that would be dealt to target."

Another question, if I set transparency to 50% (or lower), can the unit be seen by all players, or is it then considered to have perment invisibility?

no matter how high you set the transparancy, units will always see it; transparancy is only a visual effect and doesn't affect gameplay in any way.

dont know if their are any spells that makes unit not avaible to attack execpt slepp or things like that..

But you could base it on wind walk.. but the hero should still be able to attack but when he attacks you could remove the invurnebilty, i dont know if this works but anyway..

EDIT->
Hmm i just got an idea.. if you can do that other thing by trigger? why dont you change the acquisition range to 0? then the hero should't be able to attack right?.. or..¿ hmm.. anyway he will still be able to put spells on others..