I know that the Dusknoir becomes a stadium. But if you knock out say a claydol with a G attached with Darkness Lost, does it go to the lost zone or discard
It goes to the discard pile, since unown g prevents the lost zone effect of the attack.
Here's the compendium listing...
Q. If my Pokémon that has Unown-G attached to it is Knocked Out by my opponent's Giratina's "Broken-space Blow" attack or by my opponent's Giratina Lv.X's "Darkness Lost" attack, do I have to put the Pokémon in the Lost Zone?
A. No, the effect of going to the Lost Zone is prevented and you discard the KO'd Pokémon that had Unown-G attached. (Feb 12, 2009 PUI Rules Team)