Your opponent cannot target "Blue-Eyes White Dragon" in your Monster Zone with card effects.
If this face-up card is sent from the Spell & Trap Zone to the GY: Destroy all monsters you control.
You can only use the following effect of "True Light" once per turn.
You can activate 1 of these effects;
● Special Summon 1 "Blue-Eyes White Dragon" from your hand or GY.
● Set 1 Spell/Trap directly from your Deck, that specifically lists "Blue-Eyes White Dragon" in its text, with a different name from the cards you control and in your GY.