The Brain-Eating Zombie
For this part of the challenge I will (mostly) review some of my favorite HackMaster monster variants. HackMaster 4E did an excellent job in providing all the AD&D monsters a DM could probably need (and then some). We're talking more than 1600 monsters in 8 "Hacklopedia of Beasts" volumes here, with aliases and ideas for the use of special monster parts in addition to a description and the stats. And it's funny. Here's about the Brain-Eating Zombie.
I like Zombies in general and looking at the list of D&D Zombie variants, I think I'm not alone in this. It's a classic trope and, if done right, a good Zombie scenario never gets old in The Game. I even wrote a Zombie Advancement Table a while back to add to the diversity.
The Brain-Eating Zombie (aka Cranium Cracker) has a special place in my heart, though. Those Zombies are result of the strange emanation of a meteor. They are clever and fast, even able to talk or change strategies, if necessary. But all they really care for is brain. It's a classic setup. Now for the specifics.
2 HD creatures with one attack per round (for 1d8 damage) for 270 xp. First attack is always to grab the victim, every attack after that is a called shot to the head (-6). If bitten, a victim is infected if a save vs. poison is not successful and will become a Brain-Eating Zombie 24 hours later (Cure Disease and Remove Curse heal a victim completely).
It gets better.
They are pretty tough to kill. Only total dismemberment will stop them from attacking and only critical hits might affect the hp. If left for dead (that is: totally dismembered), they will regenerate completely in 2d6 days and come back to hunt down those who hacked them to pieces. Only permanent destruction of the body will avoid that. Burning the corpse will result in very poisonous fumes, killing and infecting everybody within 50 feet if a save vs. poison is not successful. Eating it's flesh will immediately infect the victim.
Normal undead immunities apply and they can't be turned (because of the alien origin...).
What to do with this?
This is a huge little monster. It's not unstoppable, but to find a suitable strategy is not easy either. It's far more classic than your basic D&D zombie. Land that meteor somewhere in your campaign setting and see what happens. Might be worth an Adventure, might change the campaign world. In the end it's an intelligent infection out for your brains. Give them a chance to conquer the world and see how they start breeding humans for brain before they run out.
Now I have to ask myself if a wizards brain tastes different than, say, a barbarians and if dwarfs and elves and some such could be infected. Or, say, not humans become infected but the dwarves have it. The result would be an intelligent dwarf zombie race out for (invent table for what specific brain they'd need, roll appropriate die) brain...