Hi, this is the scenario:

I am in my turn, I normal summon Mirage dragon, my opponent responds with BTH (bottomless trap hole) I respond to it by bringing Hand of Nepthys with Call of the haunted, and thus, ACTIVATING hand of nephtys`s special effect by offering 1 monster card other than her to bring Sacred god of Nepthys, there for BTH looses target.

Is this procedure legal play?

You cannot resolve the effect of Hand of Nephthys in the middle of a resolving chain.

1. Hand of Nephthys is not any sort of "Trigger" effect at all...it is an ignition effect...so it does not "automatically" activate when summoned.

2. You're already in the middle of resolving a chain, so you cannot activate anything while the chain is resolving.

3. Bottomless Trap Hole does not target.


Basically, no, this is not a legal procedure.