Slifer the Sky Dragon (Quarter Century Secret Rare) (RA03-EN244) - Quarter Century Bonanza 1st Edition Condition:Damaged using monsters on either field

using monsters on either field as Fusion Material

Card TextAll monsters on the field and in every Graveyard become Zombie-Type monsters

destroy 1 card on the field

(Damage calculation is applied normally)

you can Normal Summon it to have it be treated as an Effect Monster with this effect:

Slifer the Sky Dragon (Quarter Century Secret Rare) (RA03-EN244) - Quarter Century Bonanza 1st Edition Condition:Damaged using monsters on either fieldTypeDivine Beast Effect Monster AttributeDIVINE Level Rank10 Card TextRequires 3 Tributes to Normal Summon (cannot be Normal Set). This card's Normal Summon cannot be negated. When Normal Summoned, cards and effects cannot be activated. Once per turn, during the End Phase, if this card was Special Summoned: Send it to the GY. Gains 1000 ATK DEF for each card in your hand. If a monster(s) is Normal or Special Summoned to your opponent's field in Attack