Fluffal Owl

The monster effect "①: When this card is Normal or Special Summoned from the hand: You can add 1 'Polymerization' from your Deck to your hand" is a Trigger Effect that can be activated optionally. (It can also be activated during the Damage Step.)

If there is no "Polymerization" in your Deck, you cannot activate the monster effect "add 1 'Polymerization' from your Deck to your hand."

The monster effect "②: You can pay 500 LP; send the Fusion Material Monsters listed on a 'Frightfur' Fusion Monster from your hand or field to the GY, then Fusion Summon that 1 Fusion Monster from your Extra Deck" is an Ignition Effect. (You pay 500 LP as a cost to activate this effect. You cannot activate this effect unless you have a "Frightfur" Fusion Monster in your Extra Deck and the required Fusion Material Monsters for that Fusion Monster are present in your hand or on your field.)

The process of "send the Fusion Material Monsters listed on a 'Frightfur' Fusion Monster from your hand or field to the GY" and the process of "Fusion Summon that 1 Fusion Monster from your Extra Deck" are not treated as occurring simultaneously.