Ring of the Imposter

In the most recent session of the “Prophecy of the Hungry Sky" campaign, Aster rolled a 30-something when casting identify on a certain ring, so she has all the details about how it works now. Since I now don't have to worry about information leaking to my players, I can share the item with y'all and cause no end of trouble for players in any game you GM.

Ring of the Imposter

This tarnished bronze ring has a series of crude faces embossed upon it. (The “faces" may be meant to represent masks.)

This ring allows you to cast a variant of the spell alter self once per day. The effect of the ring differs from the familiar version of the spell in the following ways:

• Range: Personal Range: Touch
• In order to use the ring, you must be in physical contact with a living individual of your creature type. You mimic the form of that specific individual.
• Duration: 1 min. / level Duration: Instantaneous
• After the ring’s effect has taken hold, you are your new shape, and will remain in that form as long as you wish.
• Detect magic will therefore not show anything amiss.
• Dispel magic has no effect, for the same reason.
• You may not dismiss the effect at will, for the same reason.
• The ring will allow you to resume your true form, but it counts as your 1/day use — so if you use the ring, you’re stuck like that for the rest of the day, and when you change back, you can’t use the ring again until the next day.
• The ring “remembers” the true form of the people who use it, so that you can change back. However, you can only return to your true form if you’re wearing the ring. 
• Another ring with the same enchantment doesn’t count.
• If the form you assume has any of the following abilities… 
• You do not gain any abilities of the form you mimic, and you receive no bonuses or penalties to your ability scores.
• You retain all abilities you had before changing; however, if you do anything that the form you are mimicking would not be able to do, there is a highly noticeable visual effect.
• For example, if you mimic the form of someone who is missing an arm, and then try to use the “missing” arm, witnesses might observe a new arm growing out of the stump, performing whatever task, and then retracting.

In addition to alterations of the text of the spell, users of the ring should be aware of the following rules: 

• It is surprisingly easy to lose the ring; it has a tendency to slip off your fingers when they change shape.
• When changing, you must roll under your Dexterity in order to keep the ring on.
• If you fail and the ring falls off, you must make a DC 10 Perception check to notice you’ve lost it.
• You can choose to mimic the target’s clothing as well, but doing so requires a certain amount of mental focus.
• Roll under your Wisdom to do so successfully.
• Fail by 5 or more: Your clothes do not change at all, and probably don’t fit the new form. This is also the result if you decide not to roll.
• Fail by less than 5: Your clothes change to fit the new form, but otherwise look the same.
• Succeed by less than 5: Your clothes change, but only superficially. Close scrutiny — DC 30 Perception — will allow people to notice there is something odd about them.
• Succeed by 5 or more: Your clothes look and feel exactly like the clothes your target is wearing.
• Just as you retain all your abilities when changed, your clothing retains all of its properties, magical or otherwise.
• If you are unarmored and mimic the form of someone wearing full plate, even if you succeed in the check to have your clothes change with you, your AC will not increase; attackers may be surprised by how easily their blade splits your armor.
• The reverse is also true; someone heavily armored copying the clothing of someone unarmored may end up with a silk robe that swords inexplicably glance off of.

Note:

• You do not receive any of the target's memories; you had best dispose of the target right away, because you're going to lose any “which Jethro is the real Jethro" conflict that might arise.
• To GMs: Yes, this is basically an item that lets a villain of your choice play “doppelganger".
• And, as written, would allow, e.g., a storm giant to pretend to be a halfling while retaining every bit of its dangerous abilities, up to and including its ludicrously high strength score and ability to call lightning... imagine the results if you can delay that reveal until the worst possible time.
• To fans of a certain young adult book series: Yes, it would be hilarious if one of your PCs essentially became a nothlit as a result of this ring. For people with that sense of humor, I would suggest removing the creature type restriction and making the roll to keep the ring on much harder when changing creature types.