This card is not so good: it's waaay too situational. The thing is, even if the opponent has 2 monsters face up, he has to either
a) attack with weaker monster first
b) have 2nd monster in defence mode
Otherwise the monster you take control of will still deal damage to yourself. So if he has a 3k monster attack and you take control of his 1.6k attack monster, yeah you destroy the 1.6k monster but take 1.4k damage. Not worth it.
If you want to chain Chalice to the targeting, then yes, you cannot, as this card would be in the Graveyard already at that point.
As she is no longer on the field, Chalice is no longer able to target it, and you don't get any chance to chain with Chalice.
You must use Chalice on her when she is still on the field and the player hasn't activate her effect yet.
If we ever get this card, or if an NPC would ever use this card, it's gonna have the latest errata for sure.
As in, you need to wait until your next turn before you can use this card's effect. That is, if this card even survives being on the field until your next turn.
Zahak is the name of a person from a persian legend. That guy had snakes on his shoulders. Two snakes. Each had multi heads. This is easily a reference to that. He also killed his brother who was a king.