RAW + This errata states:
While you are wielding a glaive, halberd, pike, quarterstaff, or spear, other creatures provoke an opportunity attack from you when they enter your reach.
Say an opponent is standing 10’ away from me, and I am wielding a whip and a spear. If my opponent moves from 10’ to 5’, or 10’ to 15’ I can make an opportunity attack against them in either case. I cannot, however, make an opportunity attack when an opponent moves from 15’ to 10’. Is my understanding correct?
I’ve been looking for an answer to this for a War caster Hexblade I’m making. I want to use this to hold opponents in range of the damage dealer tanks in my party without risking my much lower health pool as much.