Buffs without abilities

Is it possible to give a unit a buff without giving it an ability?

You can have a dummy unit cast a spell on another unit to apply a buff, but otherwise no.

the best way is a tornado aura with out an icon but with a buff ^^ (but it's a ability but it don't need to be casted. and also it's kind a fake cause it may only slow (or damage ?) the targets)

ok, i'll just use an ability with the icon "black128.blp", you can't see it and justs shows an empty tooltip box when you mouse over it.
I based it off Devotion Aura (Neutral), and set it so it only effects self and gives no bonus.