Unknown G again

[fragnito]

I understand the rulings on Unknown G with effects which take place at the end of the opponents turn, but what happens if Froslass' destiny bond attack is used to a pokemon that doesnt have unknown g, and then the opponent attaches an unknown g, does the effect stay or go?

 

[PokePop]

The effect stays on Frostlass. The Destiny Bond effect sits on Frostlass until it is triggered.
When it is triggered, the Pokemon attacking Frostlass gets to ignore it if an Unown G is on it at that time.