9 official rulings from Bandai, last ruled Nov 22, 2024. Straight answers to how this card actually resolves.

Can I choose not to activate the [Security] effect of this card when my opponent's Digimon attacks?
No, it cannot. It must be activated when the opponent's Digimon attacks.
Ruled Sep 20, 2024
Can this card's [Security] effect be activated even if my Digimon and Tamer are not in the Battle Area and my Digimon with the trait "De-Reaper" is in the Breeding Area?
No, it cannot be activated. Text that does not describe which location can specify or reference a Battle Area and affects the Battle Area. In the case of this card's [Security] effect, it cannot be activated if there is no one of your Digimon or Tamer with "De-Reaper" in its trait in the Battle Area.
Ruled Sep 20, 2024
Can I use this card in my hand when I have my own face-up security?
Yes, it can be used. However, it cannot activate this effect because it does not meet the condition of the [Main] effect of this card, "if you have no face-up security of your own".
Ruled Sep 20, 2024
Can this card's [Security] effect be activated even if there is a Digimon with "De-Reaper" in its trait and a Tamer without "De-Reaper" in its trait in the Battle Area?
No, you cannot. All of your Digimon and tamers in the Battle Area must have "De Reaper" as a trait to activate it.
Ruled Sep 20, 2024
Can this card's [Security] effect be activated even if all my Digimon and Tamer in Battle Area have "De-Reaper" in their traits and my Digimon in Breeding Area do not have "De-Reaper" in their traits?
Yes, it can be activated. Text that does not describe which location can specify or refer to a Battle Area and affect the Battle Area. In the case of this card's [Security] effect, it can be activated if all of your Digimon and Tamer in the Battle Area have "De Reaper" as a trait.
Ruled Sep 20, 2024
What happens when shuffling a security that contains a security placed face up?
The security that was face up is turned back face down and then shuffled. After shuffling, the cards are not turned face up.
Ruled Nov 22, 2024
What happens to a card placed face up in security by an effect?
It becomes ostensible security and remains public. The rules are the same as for normal security, except that it is ostensible.
Ruled Nov 22, 2024
What happens when checking a security placed face down?
Checked as published. The rules are the same as for normal checks, except as published.
Ruled Nov 22, 2024
If a security placed face up is checked, does the card's [Security] effect trigger?
Yes, triggered.
Ruled Nov 22, 2024
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Questions and answers are Bandai's official rulings, collected and translated by the DigimonCardGame Wiki community and reused here under CC BY-SA. Card names and card text are © their respective publishers; Combalo is not affiliated with Bandai.