“Hyper Hammerhead”’s effect activates at the time that a monster would be sent to the Graveyard.
Even if “Hyper Hammerhead” was destroyed, its effect resolves.
The effect of “Hyper Hammerhead” can be chained to.
If you have another effect that activates at the end of the Damage Step, you can place it on a chain with “Hyper Hammerhead”’s effect (such as “Hyper Hammerhead” vs. “Hyper Hammerhead”).
Netrep Rulings:
The effect of “Hyper Hammerhead” is not a targeting effect.
The effect of “Hyper Hammerhead” activates regardless of who initiates the attack.
If “D.D. Warrior Lady” battles with “Hyper Hammerhead,” the effect of “D.D. Warrior Lady” will activate and resolve before that of “Hyper Hammerhead.