Solemn Judgment

Per-phrase breakdown

• When a monster(s) would be Summoned, OR a Spell/Trap Card is activated: Pay half your LP; negate the Summon or activation, and if you do, destroy that card. (Effect)

Judge-facing facts

• Can be activated during the Damage Step.
• Paying half your LP is the activation cost.
• Must be chained directly to the activation of a Spell/Trap Card, not to the activation of a Spell/Trap effect.
• Can only negate Summons that do not start a Chain (e.g., Normal, Flip, Synchro, Xyz, Pendulum, and Link Summons).
• Cannot negate a Special Summon that occurs while a Chain is resolving (e.g., a Ritual or Fusion Summon); you must chain this card to the activation of the card performing the Summon.

Card-specific notes from database

• A monster whose Normal, Special, Synchro, Xyz, Pendulum, or Link Summon is negated is not treated as being destroyed while you controlled it. (YGOResources)
• If this card negates a Flip Summon or the second Normal Summon of a Gemini monster, the monster is considered destroyed on the field. (YGOResources)
• If a Spell/Trap Card's activation is negated, it is not treated as a face-up card in the Spell & Trap Zone, nor is it treated as leaving the field or being sent from the field to the GY. (Konami neuron)
• You cannot activate this card to negate a Special Summon that is treated as a Synchro, Xyz, or Link Summon by a card effect (e.g., a Rank-Up-Magic Spell); you must chain to the activation of the card itself. (YGOResources)
• If a card effect performs a Summon immediately after resolution, you can activate this card to negate that Summon only if the effect was Chain Link 1. (Konami neuron)
• You cannot interrupt the procedure of a Tribute Summon to activate a Trap Card; this card is activated when the Tribute Summon is attempted. (YGOResources)