You can only use the (2)nd effect of “Predaplant Chlamydosundew” once per turn.
(1) Monsters with Prey Counters on them have their Attribute treated as DARK if they’re used as Fusion Materials.
(2) You can Fusion Summon a DARK Fusion Monster from your Extra Deck sending this card on the field along with the appropriate Fusion Materials either in your hand or on your side of the field OR monsters on your opponent’s field with Prey Counters on them to the Graveyard.