Rulings
Q1: Is the "while you have no face-up security cards" condition met when I have 0 cards in my security stack?
Yes, it does.
Q2: Can I also activate this card’s Main effect when I have 0 cards in my security stack?
Yes, you can. In such cases, you can't add a card from your security stack to your hand, therefore you only place this card in your security stack.
Q3: What happens to cards placed face up in the security stack by effects?
They become face-up security cards that remain revealed. Other than rules that specify face-up security cards, the rules apply in the same manner as standard security cards.
Q4: What happens upon a security check for a security card that is placed face-up?
The check is performed with the card left revealed. Other than rules for cards left revealed, the rules apply in the same manner as standard security checks.
Q5: Does a card's Security effect trigger upon a security check with that card placed face-up?
Yes, it triggers.
Q6: What happens if I shuffle a security stack that includes security cards placed face-up?
Any face-up cards are placed face down, then you shuffle the cards. After shuffling, all cards are left face-down.
Q7: I have just this card placed face-up in my security stack. I used my Digimon with the NSp trait to attack, and I activated the Alliance gained from this card's All Turns effect. If this card is then trashed by the 1st All Turns effect on my opponent's BT18-055 AncientTroymon, what happens to the Security Attack +1 and added DP gained from Alliance?
Even Alliance is lost, the Security Attack +1 and added DP remain.
Data Sources
Nature Spirits EX8-069 U NSp While you have no face-up security cards, you may ignore this card's color requirements. [Security] [All Turns] All of your Digimon with the [NSp] trait gain <Alliance>. [Main] Add your bottom security card to the hand. Then, place this card face up as the bottom security card. --- [Security] You may play 1 level 5 or lower Digimon card with the [NSp] trait from your hand without paying the cost.
Nature Spirits EX8-069 U NSp While you have no face-up security cards, you may ignore this card's color requirements. [Security] [All Turns] All of your Digimon with the [NSp] trait gain <Alliance>. [Main] Add your bottom security card to the hand. Then, place this card face up as the bottom security card. --- [Security] You may play 1 level 5 or lower Digimon card with the [NSp] trait from your hand without paying the cost.
Nature Spirits EX8-069 U NSp | NSp While you have no face-up security cards, you may ignore this card's color requirements. (Security) [All Turns] All of your [NSp] trait Digimon gain <Alliance>. [Main] Add your bottom security card to the hand. Then, place this card face up as the bottom security card. ---
ネイチャースピリッツ EX8-069 U NSp 自分の表向きのセキュリティがない間、このカードは色条件を無視できる。 [セキュリティ]【お互いのターン】特徴に「NSp」を持つ自分のデジモン全ては≪連携≫を得る。 【メイン】自分のセキュリティを下から1枚手札に加える。その後、このカードをセキュリティの下に表向きで置く。 --- 【セキュリティ】自分の手札から、特徴に「NSp」を持つLv.5以下のデジモンカード1枚をコストを支払わずに登場できる。