From an outsiders point of view, this is an absolutely busted effect
The Pokemon TCG: Shining Fates Collection, Pikachu V includes
[4] During Dark Yugi and the ventriloquist's Duel, the ventriloquist got the puppet to play Kaiba's cards, including "Blue-Eyes White Dragon"
SR Super Rare Lyna the Light Charmer, Lustrous X LIGHT Link 2 [ SpellcasterLinkEffect ] ATK 1850 DEF - 2 monsters, including a LIGHT monster (This card is always treated as a "Familiar-Possessed" card.) You can target 1 LIGHT monster in your opponent's GY
Mokuba Kaiba rushes into the room, asking his brother if he is okay, while Joey celebrates on Yugi taking out one of Kaiba's monsters
It means milling yourself incrementally with Altar of Dementia can tear through your deck and reanimate a bunch of creatures, building for an overwhelming Living Death