[2022] How does the Het enhancer work in relation to Arch-Glacor in hard mode? What does the +10% rare drop chance mean?

Hey! So for the Het enchancer to be active on AG you'll need to start a new streak and have the enhancer with you (this'll then mark that new streak as enhanced)
(otherwise you'd get some nasty loot rerolling if you did or didn't bring the enhancer due to it being seeded)

As for the drop chance, your unique chance is directly increased by 10%

Numbers from our drop rate post:

Streak: 1, Enrage: 999 - 1/91 chance of a unique drop

Streak: 25, Enrage: 1500 - 1/60 chance of a unique drop

With Het enhancer:
Streak: 1, Enrage: 999 - Roughly 1/82 chance of a unique drop
Streak: 25, Enrage: 1500 - Roughly 1/54 chance of a unique drop

For glacor HM specifically, you'll only need to bring it on the first kill of each streak.

if the drop rate is 1/500 the improved rate would be 1/450