At an early stage of my Lamentations of the Fallen Lords campaign, one of my players asked if there was any possibility of discovering a magic item that would help ease the heavy encumbrance of wearing plate armor. This is what I came up with.
The Glaive of Temporal Deferment is decorated on both the head and the haft with alchemical equations and poetic verses venerating a being called "Camael." The wooden haft has a slightly reddish hue. The weapon is well-crafted, and the design of the head is somewhat fanciful, with lots of intricate, abstract detailing.
Unless the wielder is the "owner" of the Glaive, it counts as an over-encumbering item, and it will be either unable to hit or unable to do damage if used to attack - some accident or coincidence will always prevent a blow from being landed, or soften the blow so that it does no damage.
To become the "owner," you must sign your name on the blade in your own blood (or make some deliberate mark or symbol in place of your name if you are illiterate or otherwise unable to write your name). The signing ritual does 1d4 damage due to blood loss and takes 1 round - it's a big signature. The signee must also mentally agree to become the owner while signing. The instructions for this process are written in tiny script on the langet, along with a note that ownership can only be relinquished through death. A new owner cannot claim the Glaive until the previous owner dies.
To the owner, the Glaive counts as an unencumbering item. If the owner is within the same 10' space as the Glaive, the owner is treated as having two less points of encumbrance.
If the owner attacks (with any weapon) while within the same 10' space as the Glaive and rolls a natural 1 to hit, the owner gains 1 point of temporary encumbrance that can only be removed through a full day of rest. It is as if an invisible force is weighing the owner down.
If the owner is reduced to less than one-fourth of their maximum HP (round down) at any point, no matter how close or far away the Glaive is from the owner, the owner gains 1 point of temporary encumbrance that can only be removed by restoring their HP to one-fourth or more of their maximum amount.*
When the owner dies, all copper, silver, and gold within 10' of the owner at the moment of death transforms into solid Osmium.
(If you think the cons outweigh the pros a bit too much to make this weapon worthwhile, you could always either make the Glaive remove more points of encumbrance or give it a small to-hit and/or damage bonus. The player who got this weapon in my campaign was happy with it as-is, though. Besides, magic items in Lamentations of the Flame Princess are generally meant to straddle the thin line between useful items and cursed ones, right?)
*Originally, I wrote the rule to state "If reduced to less than 1/4 HP (round down), the owner gains 1 point of encumbrance that can only be removed through a full day of rest," but I think the new rule above makes more sense.