As a spell or ability tries to resolve, if all its targets are illegal, that spell or ability doesnt resolve and none of its effects happen, including effects unrelated to the target
However, Gengar's popularity in Japan is significant as well, as evidenced by this Mega Dream ex's price tag
Besides that though, Luxray allows you to play around an opponents Unown G, allowing you to send up something without Unown G attached via Bright Eyes, and then send up their Nidoqueen or whatever and burn them with Blaziken FBs Luring Flame, leading to one shot Knock Out from Blaziken FB LV
In a world of where Vehicles decks are among the most powerful in the format, cards like Ishkanah, Grafwidow are great, and this isn't even including Grim Flayer, Traverse the Ulvenwald, and the rest of the powerful delirium cards in the format
Key Mouse X EARTH Level 1 [ Beast / TunerEffect ] ATK 100 DEF 100 When this card is destroyed by battle and sent to the Graveyard, you can add 1 Level 3 or lower Beast-Type monster from your Deck to your hand