So can we assume that this is the case when Demise is Ritual Summoned through the effect of Advanced Ritual Art? There is lots of confusion about whether or not a player can use a "summon-triggered" trap such as Bottomless Trap Hole or Torrential Tribute in response to the Ritual Summon through Advanced Ritual Art. I have heard judges say that the opponent would miss the timing, which I do not understand since the last line of text is "Ritual Summon the selected monster."
Answer:
The opponent can activate "Bottomless Trap Hole", assuming "Advanced Ritual Art" was the last effect to resolve on the Chain.
When "Advanced Ritual Art" resolves it Ritual Summons the Ritual Monster its controller had chosen. If that Ritual Monster's ATK is 1500 or more (and Demise has more than 1500 ATK), the opponent can activate "Bottomless Trap Hole".
Following the line of discussion in these questions, the turn player could retain priority to activate the effect of the Ritual Summoned "Demise, King of Armageddon", to which their opponent would chain "Bottomless Trap Hole".
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Curtis Schultz
Official UDE Rules Dude
CurtisSchultz_Netrep@Hotmail.com