If Ahri legend has already triggered when an enemy unit attacks, does it trigger again when Rengar is played and enters attacking during the same combat?

Ruling: Yes, Ahri legend triggers again when Rengar enters play attacking. Ahri's legend triggers the first time each unit is assigned as an attacker that combat.

Sequence:

• Enemy unit attacks, triggering Ahri legend (gives -1/-0)
• Rengar is played and enters attacking
• Ahri legend triggers again for Rengar (gives -1/-0)

Nuances:

• Ahri triggers per unit that attacks, not once per combat
• The trigger occurs the first time each unit is assigned as an attacker in that combat
• Units that enter play already attacking count as being assigned as attackers