Yu-Gi-Oh! » Rulings Q&A

"El Shaddoll Construct" has a ruling that the card's effect "At the start of the Damage Step, if this card battles a Special Summoned monster: Destroy that monster." doesn't target and is mandatory.

https://yugioh.fandom.com/wiki/Card_Rul ... _Construct

"Gravity Controller" has an effect that states : "At the start of the Damage Step, if this card battles an opponent's monster in the Extra Monster Zone: You can return both that opponent's monster and this card to the Deck."

If Player: A controls "El Shaddoll Construct" and Player: B controls "Gravity Controller" and on Player: B's turn decides to attack El Shaddol Construct with "Gravity Controller" is "El Shaddoll Construct" still mandatory chain link 1?

When two players wish to activate their "at the start of the damage step" effects, the turn player's mandatory ones will get to activate first, followed by the opponent's mandatory ones, followed by the turn player's optional ones, followed by the opponent's optional ones.

So in this case, El Shaddoll Construct will activate her damage step effect first as chain link 1 since hers is mandatory, followed by Gravity Controller's effect as chain link 2 since his is optional, assuming Gravity Controller's... controller wishes to use said effect in that same damage step.