The transformation makes the unit targetable by enemy units. Players can not target it or select it.
You don't make any sense at all =,="
You said "The transformation makes the unit targetable by enemy units", it means the transformation allows the unit to be targeted, right ?
But then, you said "Players can not target it or select it", what ???
It's like you're saying: You should drink water, but it can kill you.
I have tried your trigger, and still, I can't target Banish to the unit.
Do you mean "target", such as, the unit can be "attacked" ?
EDIT:
Okay, got it.
You meant it can be "attacked", tested it.