I've read in various guides and FAQs that Diablo II mercenaries can be resurrected from the NPC who lets you hire them; however, I can't find the option to do so. I'm in Act II and Greiz only offers the options to talk or to hire a new mercenary. What am I missing?
They can be resurrected by talking to one of the NPC folks in town... for a price.
The higher the level of your mercenary, the more expensive it will be. The maximum cost to resurrect your mercenary is 50,000 gold.
Resurrections can be performed by the following NPCs in their respective acts:
If you don't see an option to resurrect your mercenary, then you either:
You can check to see if you have one active if you press O to bring up it's stat/inventory menu.