I've been sitting on an actual play post for several weeks now involving my 4E PCs seeking out the Dread Ring in the Neverwinter Wood. There's been a session already with a couple of combats and there is at least one more session to come.
Here are the stat blocks for the creatures they have/will encounter but the stat block for the lich Valindra Shadowmantle can be found <here>.
Askarro the Unlich
I believe I came up with the name Askarro about 20 years when watching some crappy fantasy-themed movie on TV. I never used it until the second or third session of this campaign back in 2012 and it was for an undead wizard I termed an "unlich" or "lich construct" depending on how I was feeling on a particular day.
This was, of course, simply a way of having an undead spellcaster be able to return to "life" so as to become a recurring foe without having said spellcaster be as powerful as a normal lich. And Askarro is indeed a recurring foe. When the PCs first fought him he was a level 3 elite artillery. The more recent confrontation was with him as a level 7 artillery - same XP value as a level 3 elite - with the same powers but changes to his number of actions, damage, defences etc....
Suffice to say that the PCs were surprised to see him back after they defeated when they were level 2 or so. Earlier, Askarro and his undead wyvern mount had something of a roving brief over the lands north of Neverwinter. Since being "rejuvenated", he and his mount are now the chief guard dogs of the Dread Ring, tirelessly soaring above the fell location and searching for intruders which they engage in conjunction with one of more packs of werewolves (see below).
One of the things some people don't like about Paizo adventure paths is how the NPCs often have really extensive backstories that never see any actual use in play. Askarro was a bit like this for me. I had him as a thrall of Eltab and an expert in some of the magic used in the construction of the Dread Ring. (IMC, Eltab is the master of rune magic that can be used to release primordials rather than bind them: the complete opposite of the purpose of rune magic described in the runepriest entry in Player's Handbook 3.)
Despite his pact with Eltab, Szass Tam valued his knowledge and was responsible for Askarro's undead status. And that's all I will say about Askarro for now as it was and is rather irrelevant in terms of actually deploying him in combat and he is simply a combat encounter and a simple one at that: death lightning, rinse and repeat.
By contrast, Askarro's wyvern is much more tactically interesting and its ability to snatch, fly, and drop was fun to use in play. Sting of undeath also has potential but needs further development; I would love to take a fresh look at that in radiant keyword-heavy party especially where there is an invoker with radiant attacks that only damage enemies. In such a case, I would be so tempted to have the target treated as a enemy while it is subject to that effect.
Grey Wolf Werewolf
In the Neverwinter Campaign Setting, the Grey Wolf tribe of the Uthgardt are loyal servants of the Netherese who are delving the ruined city of Xinlenal east of the Dread Ring. I decided in my campaign that the Netherese had been defeated by the Thayans (frankly, I had no use for the Netherese as I had enough factions already) due to a combination of the silver-fanged treant Silvermaw and the Bones of the Thunderbeast. The Bones are the remains of an apatosaurus and are a sacred relic of the Uthgardt barbarians. The Thayans have corrupted the Bones through (clichéd) evil rituals that has also allowed them to subvert the loyalty of the Grey Wolf tribe.
And that's my long way of explaining why the Thayans are using werewolves as guard dogs.
As far as I know, the bone weird first appeared in 2E's Return to the Tomb of Horrors. No doubt inspired by the serpentine water weird, the bone weird was a snake-like conglomeration of bones animated by negative energy.
When I was thinking about creatures to include in the encounters in the Dread Ring, I wanted undead that were not common and the bone weird sprang to mind. I thought in a place like the Dread Ring where death and undeath were such real presences, that the remains of various creatures would sometimes spontaneously animate: these are the bone weirds.
I also imagined them crawling through the earth like the undead version of earthworms or ankheg and that made me think of the bulette. And looking at the stat block for the young bulette in Monster Vault, I realised that I had the creature I needed with a modicum of reskinning....
And here's another obscure 2E monster: the living wall. I first saw these in the 2E Monstrous Compendium; I have no idea where they first appeared.
I was thinking that the walls of the Dread Ring are largely ruined by the failed ritual performed there but they must have also absorbed some of the ruinous necromantic and demonic energy that was unleashed. Thinking about the walls being animated in such a fashion made me think of the living wall and then it was a matter of converting them to 4E.
The 2E version of the living wall could be incredibly complex (and powerful!) depending on what creatures it had absorbed. I decided to markedly simplify it as a monster and simply have it grab and absorb a creature and then share damage with its victim to the point where I am left with a fairly simple stat block that is definitely a soldier.
If I was going to use them again, I would consider other options such as making them lurkers and having them, much like a gargoyle, be able to assume a stony form but also to capture a creature and petrify it with them before leeching away its life force. I also thought about having it dominate a creature it absorbed and forcing it to attack.
But simple is often better and I'm rather happy with the simple stat block in this case.