The Shining Nightmarish White Light

|White Lady of Snowstorms, Sirino|||Fairy/Fusion/Effect|Water|9||2700|1800|(3 Different WATER monsters) When this card is summoned, banish all face-down cards on the field until the end phase. Banish all other monsters you control until this card leaves the field. You cannot summon another monster when you control this face-up card. When this card declares an attack, draw 1 card and reveal it. If its a WATER monster, you can discard it to banish 1 card on the field until this card leaves the field.|

|Nightmare Voice, Mysteria|||Winged-Beast/Synchro/Effect|Wind|9||1800|2700|(1 WIND Tuner + 2 or more WIND monsters) When this card is summoned, return 4 cards on the field to its owner's hand (2 of them must be yours if able). When this card inflicts battle damage to your opponent, shuffle 1 random card in your opponents hand. When this card battles a monster, you can discard 1 WIND monster to increase this card's ATK equal to half of the discarded monster's ATK during the battle. You cannot summon another monster as loong as this card is face-up on your side of the field.|

|Atmosphere Light, Wurgal|||Insect/Ritual/Effect|Light|9||2500|2900|You can Ritual summon this card by using any ritual spell card (you need to tribute LIGHT monsters to Ritual summon this card and treat the level of all monsters tributed as its original level). When this card is summoned, shuffle all other monsters you control to the deck, then draw the same amounts of cards from your deck. If you draw a LIGHT monster, you can discard it to banish 1 card your opponent controls. When this card destroys a monster by battle, reveal the top card of your deck. If its a LIGHT monster, banish it and 1 card on the field. You cannot summon another monster as long as this card is on the field.|

|The Shining Darkness, Lumia|||Fiend/Xyz/Effect|Dark|3||900|500|(3 level 3 DARK monsters) This card is also treated as a LIGHT monster on the field. You cannot summon another monster as long as this card is face-up on the field. WHen this card is summoned, you can discard 3 DARK monsters from your hand. This card gains ATK equal to the sum of the discarded monster's level x 300. Once per turn, you can detach 1 Xyz material from this card to draw 1 card. If its a DARK monster, attach it to this card, then destroy 1 face-down card on the field.|

(2 of them must be yours if able).

"must" and "if able" seem like a contradiction.

it means, if you only have the monster on your side of the field, you can return any 4 cards on the field.

this prevents the effect from fizzling if the above scenario happened.