I have a bunch of stuff coming down the pipe (if you could only see my drafts folder…), but I was talking with one of my players about something completely unrelated to D&D and had a flash of inspiration. What if you created a group of magic items that were much like immurements from Adventurer’s Vault 2, except that they transformed the character – both physically and mechanically – into a monster? It’s that second half that’s important here, because powers that “change you into something” already exist. They grant you new abilities and change certain stats, but very few of them limit your access to your everyday powers.
I think the real value of these items is when they’re used as one-offs and consumables, because then they don’t become part of the routine. The players should never say, “Oh, it’s a boss fight, I think I’ll turn into a dragon.” I also think that the monster should be custom fitted, because there are some monsters that shouldn’t be included and because it allows you to maintain theme more tightly.
Just as I mentioned in my article on replacement fights, there are some players who don’t like the idea of “wasting time” playing something other than their character. To their way of thinking, they put all that effort and investment into the character so they could, you know, actually play the character. These types of players are unlikely to need a “break” from their character and are unlikely to perceive much value in a replacement fight.
Transformation fights also have two weaknesses that a replacement fight does not. First, the PC monsters in a replacement fight don’t have to be tuned to the characters because none of the characters are present (I think this actually a strength of the replacement fight). When you transform one or more characters, you have to make sure that the PC monsters are neither overwhelming nor insignificant to the encounter. This can be challenging to achieve.
The other concern is monkey-wrenching party synergy. Let’s say that you add a magic item that transforms a character into a brute, which is most analogous to a melee striker. If the Barbarian uses the item, it’s not much of a swap, which might or might not be okay. If the Paladin uses the item, the party is suddenly less one defender, which might throw them out of whack a little bit. The transformation will generally be less jarring if the transformation makes the fight easier or is just thrown in for a bit of fun, rather than being the key to the fight. Put another way, giving the players access to transformation is almost always more fun if the transformation is on their terms.
While I think it’s better to have the item turn someone into a specific monster, doing it this way does introduce a certain amount of “freshness dating.” Becoming a level 13 angel is awesome when you’ve just hit the paragon tier. It’s much less so at 15 or 16.
Just as an aside, I don’t include the cost of rare items because I think they should never be for sale. Your mileage may vary.
I tried just making the items, but not having established rules made the cards cumbersome.
The Rules of Metamorphosis
- When you metamorphose, your character is removed from play and replaced with the monster. This means that you only have the characteristics, powers, etc. that are listed on the monster. You do not retain any powers, class features or equipment.
- While metamorphosed, you are the monster. No checks or powers will reveal you unless they specifically detect transformation. You might have to make checks to behave properly or to mimic a specific individual.
- When you metamorphose, you spend a number of healing surges listed on the item. The monster has hit points equal to that many multiples of your healing surge value .
- When you metamorphose (either way), all effects on you end. Similarly, all your sustained effects immediately end .
- The monster is never considered bloodied (this may be a consideration when transforming into certain creatures. 
- The monster may not spend healing surges for any power or ability that is not listed on the monster.
- You leave the form at the end of the encounter (or after an hour out of combat), when you are reduced to zero or fewer hit points or when you use a minor action to end the transformation.
- When you leave the form, the monster is removed from play and your character returns to play in any space the monster occupied.
- When you leave the form by being reduced to zero or fewer hit points, you do not fall unconscious nor do you trigger powers or effects that trigger off something being reduced to zero or fewer hit points.
Most of the time, the player will be in complete control of the monster, though there are some circumstances in which limits are a good idea. If you look at the examples below, the player should have free rein with the golem, but the angel shouldn’t do anything “unangelic.” If you’re going to place these limits, let the player know in advance. The last thing you want is a return to the bad old days of “your character wouldn’t do that.”
 – This is done to prevent a situation where the character “superpads” himself by transforming into a monster with full hit points with only the item activation as an opportunity cost. You could, if you wanted, have the monster have the same hit points as the character it replaces and track hit points across transformations, but that enters the grey area where you’re blending character and monster stats.
 – While this has the potential for a small amount of abuse, it simplifies things. It’s also a natural byproduct of leaving and reentering play, but makes for a nice clarification.
 – This is done for simplification. Alternatively, you can have the monster’s bloodied value be equal to half the hit points it started with.
The Mask of a Million Faces
The Mask has been known by many names. It has been passed down from assassin to cutpurse to psychopath for generations. It has never been a force for good, rather the opposite.
Design Theory: This is an example of what I consider to be the least viable item of this type. I suppose I could have put a WARNING! icon on it, because I think it will distort your game, but you’re all big girls and boys. Unless and until it gets out of hand, I suppose this item could be a lot of fun. You could easily make a level 20 version for paragon tier humanoids and a level 30 version for epic, though those versions would have far fewer options available to them.
As a further warning, while I would feel comfortable making variants of this item that open up beasts, demons and the like, I would probably not make one that transforms someone into an undead creature. Those monsters are (ostensibly) balanced around the idea that at least one person in the party will have access to radiant damage and/or a power that specifically hurts undead. This is generally not true of NPCs.
I think this design is weak in a couple of ways. First, some players are going to always want to change into a monster of their level, something that may not always be available. Restricting them to monsters of their level or lower, however, is part of how you firewall against problems like the level 6 character who turns into a level 10 monster and wrecks an encounter. If your players are asking for modified versions of standard monsters to match their level, this will be more work for you.
The Apparatus of Sanal Malysi
Sanal Malysi is better known for having created the first Warforged. The apparatus was simply an early proof-of-concept. The battered hulk can still fight, despite having been in service for centuries.
Design Theory: I happen to think that the monster itself is a little vanilla, but it makes a decent starting point. Whether or not it feels exciting will depend largely on the circumstances in which it is deployed. Being able to spend up to three healing surges is intended to allow the apparatus to feel more like a “real” defender. Note that if Mailed Rebuke hits after being triggered by an attack, it will not cancel the attack (at least that’s my understanding of the interaction).
If I were going to include the apparatus in my game, I would probably have the PCs sneak into the enemy camp to steal it. Because the horses that pull the cart are elsewhere, someone has to get in the apparatus and walk it back to friendly lines.
Design Theory: I don’t know which way I would enjoy this item more. On the one hand, it could make for an amazing “oh yeah, well then I turn into an angel!!!!” moment when the party is fighting demons or undead. Sometimes the PCs just get to be cool. On the other hand, it might be fun to just give the characters one and wait to see when they use it.