Hieratic Dragon of Gebeb

The effect "When this card destroys an opponent's monster by battle and sends it to the Graveyard: You can choose 1 Dragon-Type Normal Monster from your hand, Deck, or Graveyard, and Special Summon it, but its ATK and DEF become 0" is a Trigger Effect that activates on the field. (This effect does not target. You choose 1 Dragon-Type Normal Monster to Special Summon at the time of effect resolution, and Special Summon it as a monster with 0 ATK and 0 DEF.)

The effect "Choose 1 Dragon-Type Normal Monster from your hand, Deck, or Graveyard, and Special Summon it, but its ATK and DEF become 0" is an effect that must be activated when "Hieratic Dragon of Dragon-Gev" destroys an opponent's monster by battle and sends it to the Graveyard (i.e., at the end of the Damage Step).

If "Hieratic Dragon of Dragon-Gev" battles a monster with the same ATK and both are destroyed, the effect "Choose 1 Dragon-Type Normal Monster from your hand, Deck, or Graveyard, and Special Summon it, but its ATK and DEF become 0" does not activate.

The effect "When this card is Tributed: You can Special Summon 1 'Hieratic' Normal Monster from your hand, Deck, or Graveyard" is a Trigger Effect. (This effect does not target.)

The effect "Special Summon 1 'Hieratic' Normal Monster from your hand, Deck, or Graveyard" is an effect that must be activated if "Hieratic Dragon of Dragon-Gev" itself is Tributed. It activates not only when Tributed by a card effect, but also when Tributed as a cost to activate a card's effect, or when Tributed for an Advance Summon. (It also activates during the Damage Step.)