This effect targets 1-3 cards you control.
If you control your opponent's card, you can target it with this effect. The card will return to your opponent's Deck and will count towards the number of cards your opponent must discard at random and the ATK gain for this card.
If you target a Fusion or Synchro Monster with this effect, it returns to the appropriate Extra Deck and still counts towards the number of cards your opponent must discard and the ATK gain for this card.
If you use "Shrink" on "Earthbound Immortal Wiraqocha Rasca" its original ATK becomes 50, but it retains any ATK gained from its own effect.
If you choose to return a Field Spell you control to your Deck with the effect of "Earthbound Immortal Wiraqocha Rasca" you will return the card to your Deck, your opponent will discard as appropriate, this card will gain the appropriate amount of ATK, and then it will destroy itself by its own effect.
If "Skill Drain" is activated, this card loses any ATK gained from its effect and will not regain it even if "Skill Drain" later leaves the field.
If this card is turned face-down by a card that is chained to its effect, cards will still be returned to the Deck and your opponent will still discard, but this card will not gain any ATK.
If your opponent has fewer cards in hand than the number of cards you return to the Deck when this effect resolves, all of their remaining cards are discarded and this card will gain ATK only for each card discarded.
If your opponent has no cards in hand when you Normal Summon this card, you cannot activate its effect.