Who likes versatility?
With the official release of Eberron: Rising from the Last War comes the formal addition to D&D canon of the Changeling race. As a people, they have always been an interesting concept. Descended from Doppelgangers, they are the ultimate race for blagging their way into enemy territory and stealing secrets due to their ability to mimic the appearance of other creatures of a similar size. While other races can do this perfectly well, assuming they have a spell like Disguise Self available, Changelings can do it for free.
In Eberron lore, Changelings often served as spies, using their natural ability to appear as whoever they wanted to be to gather information on the down-low. As a result of this, the general level of paranoia in Eberron is high, and Changelings themselves are regarded with suspicion. It may be worth spending some time thinking about how your Changeling might deal with a situation where no-one will trust them no matter what they say!
On top of that, they come with a good deal of options for players, both in terms of game mechanics and character design. This freedom of choice comes in a slightly less subtle and simple way than it does for some other races (Tieflings, I'm looking at you!) Nonetheless, a Changeling can be almost anything you want them to be... but first, let's look at what they're naturally rigged up to specialise in.
A familiar face
Before we jump into the more mechanical section of the guide, it's worth saying that this is not necessarily a recommended build, and you should in no way feel that this is the only viable way to build your Changeling. As with all other races, it's not necessary to optimise everything to be able to enjoy playing the game (although if you like a bit of min/maxing then have at it!).
The primary stat bonus that Changelings enjoy is to Charisma, and their racial skill proficiencies all lean towards the social side of the game. As mentioned above, when combined with their ability to literally change into a different person, this really gives a member of this race a huge advantage when it comes to getting the party access to those difficult to reach places.
Combined with the Actor feat, you've basically given yourself carte blanche to go anywhere you like. Need to sneak into the duke's chateau to steal some papers? Change into the duke, walk in and get them unhindered! Need to get a group of enemy guards off your six? Turn into their captain and tell them to stand down! Between racial skill proficiencies and a feat that gives you advantage on checks where you're trying to pass yourself off as another person, your luck should be in (disclaimer, I am not responsible for natural 1s). Of course, the Actor feat relies on you having seen and heard the person you want to mimic, but... when you can easily morph yourself into a rank and file peon wearing the appropriate ensemble to blend in with the right crowd... how hard could that be?
With the secondary bonus available to assign to the stat of your choice, Changelings make ideal Bards, Warlocks, Sorcerers and Paladins (although depending on the subclass of Paladin, walking around wearing a plethora of different faces might seem a bit out of character). Bards, Warlocks and Sorcerers all have access to mind-bending spells like Suggestion, too, so once you're best buds with the big bads you can start whispering things in their ear, sprinkle a little magic on it, and hey presto – they're dancing to your tune.
Be who you want to be
With all of that said, though, the fact that you're able to boost a stat of your choice means that Changelings can be viable for any class. Being able to hit the magic 16 for your primary stat on a point buy build is the secret to making your class viable. If Charisma isn't it then you can either dump it and still have a decent score, or you have the added bonus of being able to talk your way out of whatever situations you've gotten yourself into. In this way, the class has been designed to be every bit as much of a chameleon mechanically as they are in game. You get to choose what you want to do and what you want to be, and build accordingly! Feeling roguish? Boost your Dex and go for broke. How about Cleric? Give Wisdom a bump and you'll have both divine power and the ability to bring people around to loving your deity through your likeable nature.
On top of that, this is the ideal class to choose if you can't decide between a few different character designs. If you're the type of person that ends up drawing and redrawing your character because you're never fully happy, you now have a mechanic in game that facilitates this, along with an anchor in lore that explains why you never appear to look quite the same two days in a row. Changelings see altering their appearance as a way to express artistry, which perfectly mirrors their player doing the same as they hunt for what they see as the perfect design.
What you may not have noticed
There is one quirk in the Changelings' rules that's worth mentioning in case you missed it (for all of you fans of playing with the Rules As Written). Taking on the appearance of another creature requires you to use your action. Once you do it, you keep that form until you use an action to change back, or you die. There is nothing that facilitates changing directly from one form to another, meaning that you will need to spend one round as a pale, colourless creature that probably looks very different from everyone else around it before you can take another action and shift into your new choice of form. Six seconds isn't long, but if you're spotted by someone then expect a lynch mob to be on your tail in no time!