Ask Eko to get ready to do a variety of divinations quickly just inside the ward. Ask if he knows any life magic - if not, tell him that what we noticed of the creatures last time might have been a side effect of the sense vitality spell we'd used to determine the health of the children, a spell that every elf learns - or it might be something else. You have some spells of your own that you'd like to try to detect and interact with the things you sensed before. You DID definitely sensed them, and you're going to see if entering the woods doesn't allow you to sense them again, but you're going to be close enough to the edge that you can call for everyone to retreat if they get too close and still have time to get out. When you do that, you want Eko to be ready to cast any detection of his own he can do, without putting himself into any undo danger, while providing him with the most details you can about the exact location of the things he's supposed to be sensing. Mention that at the very least, your pursuers seem to be making efforts to avoid physical obstacles, going around them - it would definitely be worth setting up a physical barricade to see if it's possible to capture or at least slow down one of these creatures, giving you more time to study it.
You outran them last time, and you won't be going nearly so deep this time.
If you have no luck with this, you'll start camping just inside the wards hoping to lure them out, until you're out of mana at least. But the key is that you're going to try to get their attention and draw them out.
Also, ask if all of this other guys spells were cast from inside the wards - maybe the wards were somehow interrupting the detection magic? Mention that you could no longer sense the vitality of your pursuers once you were outside the forest, indicating that the wards may be blocking your ability to detect them as well as their ability to detect you.
So, Goals:
We've got an improved version of detect vitality, which we might be able to use with our necromantic sight to really figure out more of what's going on with these creatures... IF we can get their attention. We should bring Omo with us, and talk about what's going on away from Eko's ears and talk about larger plans.
If we fail to draw any attention...
Search the woods for animals. Are there any? Bugs, even? Why does this force seem to target people - are the trees flatlined in the same way somehow? Without bugs to pollinate them, how do they spread and persist? If we can detect animals, do they differ from the kind of animals outside the ward - is it only smaller animals or something?
Gather information of this sort.
A reminder of our last encounter:
Suddenly, you whip your head around, searching behind you in the forest. Coming up behind you is a source of Necromantic Energy- three Vitality's worth, forty five feet away but moving fast, coming straight at you.
...it is definitely Necromantic...
..As you duck between the trees and jump over shadowy roots, you glance over your shoulder, trying to get a better idea of what exactly you're fleeing from. Unlike the zombies, your pursuer sheds no light on its surroundings- you catch glimpses of purple only because of your Necromantic Sight. It doesn't seem to be very large, whatever it is- about as big as a dog, rumbling easily along the forest floor...
...A long, rotted log suddenly looms in the darkness, but you easily climb over while Omo hurdles it without even breaking stride. As you rush through the trees, you see that your pursuer has a much more difficult time of it, taking the long way around the obstacle...