Like many DMs, when I gift a magic item to the party, I want it to be memorable. Often, I do this by tying the item thematically to the foe in which the party is facing down. Evil Necromancers and the undead are classic monsters that just never seem to get old. Maybe you are playing Descent into Avernus or the latest Pathfinder adventure: Hellknight Hill (look for a review coming shortly on that!). These villains have made pacts with outside forces and have surely been granted special war-gear in order for-fill their evil plot. And nothing says evil like bone infused armor! So, here are a few of my favorite undead armors from the D&D 3.5 Magic Item Compendium. Keep it mind, with minor tweaks, these items can be used with any system or edition.
Prepared from the remains of an animated skeleton, this armor covers the upper body with a white, rib-like structure that resembles bleached bones. Large Skulls serve as epaulets. – 3.5 Magic Item Compendium
This item acts as a magic +1 to AC breastplate. The wearer also receives resistance to slashing/piercing damage. In addition to bone armor just being freaking cool, the Exoskeleton armor can help a marshal character take a bit more damage if they enjoy that bash-in-the-door style of play. You could also give bonuses to intimidation checks against the living as I imagine wearing an exoskeleton would make a person think twice before messing with you. Also, I doubt many adventurers are sporting such an outfit, so perhaps the character that dons the armor gains a bit of a reputation for being the bad-ass that slew the evil plaguing their lands? Always try to add that special touch that is unique to your game.
Ghoul Shell Armor:
This armor consists of shaped and fitted sections of ghoul flesh sewn together around a chest-piece that is emblazoned with a gaunt face. – 3.5 Magic Item Compendium
Beside being mildly gross, the Ghoul Shell Armor acts as magical leather armor with a +1 to AC. It also allows the wearer to cast the Ghoul Touch spell up to three times a day. This spell allows you to paralyze a living target and could be extremely useful for the Rogue of the party. I would add an additional affect that Ghouls see the wearer as one of their own. Upon inspection of course the Ghouls try to eat your insides.. so you know, be reasonable. With any of these undead themed items, you could work in a small curse. I don’t like to overly punish players when they receive a magic item, but a fun curse could be that the wearer craves flesh from time to time. Something that allows for fun role play, but doesn’t make the player feel like they got screwed or the item is worthless.
Vampire Hide Armor:
This armor is decorated with fangs and spikes. A gaunt, skull-like face with bat wings at the temples decorates the chest-plate. – 3.5 Magic Item Compendium
If your party does face a vampire and lives… well, lives without becoming vampires, then they certainly deserve to be rewarded with cool magic items. Vampire Hide Armor acts as studded leather with a +1 to AC, but also grants resistance to silver and necrotic damage. To add flavor, I would also grant a bonus to grapple checks in order to pin your target. A bonus to diplomacy and/or charisma would also feel appropriate for such an item. Player power is something that DMs will always have to balance, and I often lean toward providing more minor abilities that feel thematic rather than large numerical gains. If the players receive this Vampire Hide Armor from a higher level creature, then you could add an affect that allows the wearer to transform into a bat or sprout black bat wings so they may fly once per day. Books, and articles like this, are wonderful for inspiration, but always feel free to put your own twist on it.