Eternal Soul

Per-phrase breakdown

• Every "Dark Magician" in your Monster Zone is unaffected by your opponent's card effects. (Continuous-like)
• If this face-up card leaves the field: Destroy all monsters you control. (Trigger-like)
• You can only use the following effect of "Eternal Soul" once per turn. (Condition)
• You can activate 1 of these effects; ● Special Summon 1 "Dark Magician" from your hand or GY. ● Add 1 "Dark Magic Attack" or "Thousand Knives" from your Deck to your hand. (Quick-like)

Judge-facing facts

• Continuous Trap Card.
• The effect making "Dark Magician" unaffected by opponent's card effects does not start a Chain Link.
• The effect to Special Summon or add a card to your hand starts a Chain Link. You choose which bulleted effect to apply at activation.
• The effect to destroy all monsters you control is a mandatory effect that starts a Chain Link. It activates even during the Damage Step.
• You can activate the card without activating its bulleted effect, or activate the card and its bulleted effect in the same Chain Link. Neither can be done during the Damage Step.

Card-specific notes from database

• The destruction effect activates if this face-up card is sent to the GY, returned to the hand, or banished face-up. It does not activate if returned to the Deck or banished face-down (Konami neuron).
• If the card activation of "Eternal Soul" is negated and destroyed, its effect to destroy your monsters does not activate because it is not considered to have left the field (Konami neuron).
• If "Eternal Soul" is destroyed by an effect chained to its card activation, its effect to destroy your monsters does activate (Konami neuron).
• "Solemn Warning" can only be chained to the card activation of "Eternal Soul" if the effect to Special Summon "Dark Magician" is activated in the same Chain Link. It cannot be chained to the card activation alone, or to the effect activation of an already face-up copy (YGOResources).
• A "Dark Magician" unaffected by opponent's effects due to "Eternal Soul" cannot be used as Fusion Material for the opponent's "Super Polymerization" or "Fallen of Albaz" (Konami neuron).
• You can Special Summon "Dark Magician the Dragon Knight" from the GY with this effect if it was properly Special Summoned first (Konami neuron).
• If "Eternal Soul" is Set as a monster by "Magical Hats", its effect activates if it is flipped face-up and destroyed, but does not activate if destroyed while face-down (YGOResources).
• If "Destiny HERO - Plasma" is applying its effect, a Special Summoned "Dark Magician the Dragon Knight" has its effects negated, so its name does not become "Dark Magician" and it is not protected by "Eternal Soul" (YGOResources).