Can Ahri leader give -1 to every unit attacking, and can the effect be used multiple times per turn since it doesn't say to tap Ahri?

Ruling: Ahri's effect triggers every time someone attacks into Ahri's battlefields, and every attacking unit gets -1. The effect does not require tapping and triggers separately for each attacking unit.

Sequence:

• When a unit attacks into Ahri's battlefields, Ahri's effect triggers
• That attacking unit gets -1
• If multiple units attack, the effect triggers once for each attacker
• Each trigger can be interacted with separately

Nuances:

• If a single unit attacks twice in one turn, the effect stacks (the unit would get -1 each time it attacks)
• If 5 units attack, Ahri triggers 5 times, once for each individual attacker