What is slifers effect?

Slifer the Sky Dragon

Divine-Beast/Effect/10/DIVINE

ATK/DEF: X000/X000

Actual Lore: The heavens twist and thunder roars, signaling the coming of this ancient creature and the dawn of true power.

In-Game Lore: You must Tribute 3 Monsters you control to Normal Summon this card. The Normal Summon of this card cannot be negated. When this card is Normal Summoned, a Spell, Trap, or Effect Monster Card cannot be activated. This card cannot be targeted by the effects of a Spell, Trap, or Effect Monster. If this card is Special Summoned, it is sent to the Graveyard during the End Phase. The ATK and DEF of this card becomes the number of cards in your Hand x 1000. When your opponent Normal Summons or Flip Summons a monster(s) with 2000 DEF or less, destroy the Summoned monster(s).