Edison format ruling
Dark Nephthys

Card effect (current official text)If you have 3 or more DARK monsters in your Graveyard and this card in your hand: You can banish 2 of them from your Graveyard; send this card from your hand to the Graveyard. During your next Standby Phase after this card was sent to the Graveyard by this effect: Special Summon this card from the Graveyard. When this card is Special Summoned: Target 1 Spell/Trap Card on the field; destroy that target.
Rulings
- Dark Nephthys' first effect is an Ignition Effect. Removing DARK monsters from play is a cost.
- You can activate Dark Nephthys' first effect while Banisher of the Light or Macro Cosmos is face-up, but Dark Nephthys will be removed from play.
- Dark Nephthys effect to Special Summon itself starts a Chain.
- The owner of Dark Nephthys Special Summons it, even if their opponent activated its first effect.
- Dark Nephthys' third effect activates whenever it is Special Summoned, including by another card's effect. It is not optional.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Edison forum — sourced change requests get reviewed.