The "While this card has Xyz Material, neither player can send cards from the Deck to the Graveyard, and any card that returns from the Graveyard to the hand is banished instead." effect is a Continuous Effect.
The "During either player's turn, when an opponent's DARK monster activates its effect: You can detach 1 Xyz Material from this card; negate that activation, and if you do, destroy it." effect is a Quick Effect. (Detaching 1 Xyz Material from this card is a cost to activate this effect. It can be activated during the Damage Step.)
This effect does not target. It must be chained directly to the activation of the effect of a DARK monster. It can also be activated in a chain to the effect of a DARK monster activated outside the field like the hand or Graveyard.