If I place Hexdrinker on Irelia, does that mean Deflect doubles?

No, placing Hexdrinker on Irelia, Fervent does not "double" the Deflect keyword in the sense of multiplying the value. Instead, the Deflect values are summed.

According to Rule 809.2:

"If a Unit has Deflect, or has been granted Deflect, and is granted Deflect by an additional source, the Deflect Value of all granted Deflect keywords is summed."

Here is how it works for your units:

  • Irelia, Fervent has the Deflect keyword (which defaults to a value of 1 per Rule 809.1.b.3).
  • Hexdrinker grants the Deflect keyword (also a value of 1).
  • When equipped, Irelia will have a total Deflect 2.

As noted in RiftJudge FAQ 619, Deflect values stack when multiple sources grant the ability.