I think I know how this should play out, but I wanted to be sure.

A hero has a Guard order, on the OL turn a skeleton moves to attack him and he interrupts. The skeleton revives courtesy of Undying.

The question is, does Undying end the skeleton's activation, or can he complete his turn? I say that the skeleton can still make his attack, because the activation was interrupted, and nothing says that Undying ends the monster's turn.

How say you all?

ronin3338 said:

There is absolutely nothing that might even hint Undying could end the monster's turn. It might be suggested that dying ends the monsters turn (with no foundation in the rules mind you), however all you have to do to counter that little piece of fantasy is read the rules.
DJitD Pg23
...An Undying figure must stay dead in order for effects that take place when it is “killed” to actually occur.
So even if being killed did have the effect of ending the monster's turn, if it un-dies then that effect does not take place.

Fully agree with Corbon's assessment.

Thank you for your prompt replies, which confirm what I thought.