Suppose your opponent has Light and Darkness Dragon out.

I can discard 1 card from my hand to special summon Swap Frog, right? LDD shouldn't negate it because discarding 1 card to summon Swap Frog is not really activating it's effect. It's just summoning... I think.

Let's suppose the monster I discarded was Nimble Angler. Nimbler Angler activates first... and then I choose to activate Swap Frog. Of course, JDD kicks in... but the question is this. What effect does JDD negate? Does it negate Angler or Swap Frog.

Let's also say, later on, I attack JDD with Catastor. JDD has 2300 ATK at this point. Catastor activates at the start of the damage step. LDD then activates, negating Catastor but lowering its ATK 2300 --> 1800. The damage step continues and Catastor kills JDD in battle. Is this correct?

Here is the duel below for context.


Round 1

K’s turn
• Draws (hand 6)
• Activates Gold Sarchophagus: banishes Tidal, Dragon Ruler of Waterfalls
• Activates Tidal: adds Steam to hand
• Activates Steam, Dragon Ruler of Droplets: discards itself and Eclipse to special summon Tidal, Dragon Ruler of Waterfalls from deck
• Activates Eclipse Wyvern: banishes REBMD from deck
• Special summons (banishes Steam + Eclipse) Blaster, Dragon Ruler of Infernos:
• Activates Eclipse, adds REBMD to add
• Xyz summons (Tidal + Blaster) Mecha Phantom Beast Dracossack
• Activates Dracossack (detaches Blaster): special summons 2 Mecha Phantom Beast Tokens
• Normal summons (tributes Tokens) Light and Darkness Dragon

Sophia’s turn
• Draws (hand 6)
• Special summons (discards Angler) Swap Frog
• Activates Nimble Angler…
o K activates LDD…
• Activates Swap Frog: mills Ronintoadin
o LDD resolves… negates Angler (ATK 2800 → 2300)
• Normal summons Genex Controller
• Synchro summons (Swap Frog + Angler) Ally of Justice Catastor
• Catastor attacks LDD…
o Activates Catastor…
o K activates LDD: Catastor negated (ATK 2300 → 1800)
o …Catastor destroys LDD (LP 4000 → 3600)
• K activates LDD: destroys all monsters and special summons Blaster
• Sets 1 S/T
• Activates Ground Collapse: crushes 2 Monster Card Zones
• Ends turn…
o At end phase, K’s Blaster returns to his hand

Round 2

K’s turn
• Draws (hand 5)
• Standby phase: Gold Sarchophagus (1 turn)
• Banishes Tidal and LDD to special summon Blaster
• Activates Different Dimension Reincarnation: discards Eclipse, special summons Tidal
• Activates Eclipse: banishes Tempest
• Activates Tempest, Dragon Ruler of Storms: adds Lightning from Deck to hand
• Xyz summons (Tidal + Blaster) Big Eye
• Activates Big Eye (detaches Tidal): controls Catastor
• Normal summons Lightning, Dragon Ruler of Drafts
• Special summons (banishes Lightning) Red-Eyes Darkness Metal Dragon*
• Catastor attacks Sophia (LP 4000 → 1800)
• REDMD damages Sophia…
o Sophia activates Weeping Stone: damage is negated, she mills a monster
o Sophia activates Nimble Angler: Special summons Nimble Manta and Nimble Sunfish

*can’t activate it, even though he wants to. Is too immersed in his programmed thinking

Sophia’s turn
• Draws (hand 2)
• Xyz summons (Manta + Sunfish) Ghostric Socuteboss
• Activates Socuteboss (detaches Sunfish): destroys REDMD, crushes Monster Card Zone
• Activates Salvage: returns Swap Frog and Angler to hand
• Special summons (discards Angler) Swap Frog
• Activates Angler: Special summons Nimble Manta and Nimble Sunfish
• Xyz summons (Manta + Sunfish) Ghostric Socuteboss
• Activates Socuteboss (detaches Sunfish): destroys Big Eye, crushes Monster Card Zone
• Activates Swap Frog: mills Dupe Frog
• Activates Ronintoadin: banishes Dupe Frog to special summon itself
• Xyz summons (Swap Frog + Ronintoadin) Ghostric Socuteboss
• Activates Socuteboss (detaches Swap Frog): destroys Catastor, crushes Monster Card Zone
• 3 Socutebosses all attack for game.

1.) Yes, Special Summoning Swap Frog via its effect is an inherit Special Summon effect that does not start any Chains, so Light and Darkness Dragon cannot Chain to negate the effect.

2.) Light and Darkness Dragon only negates whatever it activated in direct response to. In this case, being a mandatory effect, it would be activating in response to Nimble Angler.

3.) Yes.

Ally of Justice Catastor: The effect of "Ally of Justice Catastor" will activate when it battles a monster with multiple Attributes, such as "Dark Simorgh" or "Light and Darkness Dragon". If "Light and Darkness Dragon" negates this effect, then damage calculation if performed as usual.