At the beginning of your draw step, draw an additional card
(Equipment, Auras you control, and counters are modifications.)

Card Set(s) -ONE PIECE CARD THE BEST- [PRB-01] CARD VIEW ST03-008 | C | CHARACTER Trafalgar Law Attribute Slash Block Icon 1 Type The Seven Warlords of the Sea/Heart Pirates Effect [Blocker] (After your opponent declares an attack, you may rest this card to make it the new target of the attack.) Card Set(s) -ONE PIECE CARD THE BEST- [PRB-01] CARD VIEW ST03-008 | C | CHARACTER Trafalgar Law Attribute Slash Block Icon 1 Type The Seven Warlords of the Sea/Heart Pirates Effect [Blocker] (After your opponent declares an attack, you may rest this card to make it the new target of the attack.) Card Set(s) -ONE PIECE CARD THE BEST- [PRB-01] CARD VIEW ST03-008 | C | CHARACTER Trafalgar Law Attribute Slash Block Icon 1 Type The Seven Warlords of the Sea/Heart Pirates Effect [Blocker] (After your opponent declares an attack, you may rest this card to make it the new target of the attack.) Card Set(s) -ONE PIECE CARD THE BEST- [PRB-01] CARD VIEW ST03-013 | C | CHARACTER Boa Hancock Attribute Special Block Icon 1 Type The Seven Warlords of the Sea/Kuja Pirates Effect [Blocker] (After your opponent declares an attack, you may rest this card to make it the new target of the attack.) Trigger [Trigger] Play this card

While they might not help the mill plan specifically, they are instrumental in ensuring you stay alive to execute it
Card draw spells like this tend to be perfect fits as a result
This dragon hydra is efficient in almost any point of the mana curve, and its been a staple of aggressive red decks in Standard ever since it was printed