Yes, in Dungeons & Dragons 5e, Changelings are generally immune to the Polymorph spell due to their racial trait, and they possess strong mental defenses making them resistant to psychic/charm effects, but they aren't inherently immune to everything like diseases or poisons unless specific traits are added, though they can often resist poisons better than other humanoids. Their nature as "Shapechangers" makes them a special case for certain magic, notesReddit users.
WotC has confirmed that changelings are considered to have the Shapechanger subtype. So they are indeed immune to polymorph and can be affected by moonbeam.
They had an innate resistance to sleep and charm magic. A changeling spoke softly, but when they talked to someone they had a knack for getting them to give away more information than they intended to share.
Absolutely. The whole changeling thing that they were vulnerable to "cold iron" (cold iron and regular iron are two completely separate things) was something from an entirety separate game system based on also on some traditional Celtic lore.)
Curse of Lycanthropy sticks. Also works on shifters, the descendants of lycanthropes. Intentionally so, Lycanthropy is an incredibly potent curse. Changelings are immune to stuff like polymorph against their will however.
Among the diseases or disabilities with symptoms that match the description of changelings in various legends are spina bifida, cystic fibrosis, PKU, progeria, Down syndrome, homocystinuria, Williams syndrome, Hurler syndrome, Hunter syndrome, autism spectrum disorder, Prader-Willi Syndrome, and cerebral palsy.
Each ability score (Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma) begins at a base score of 8. Players have 27 points to distribute among their ability scores.
Ageing slightly faster than humans, changelings are considered mature at around age 15 but have roughly the same lifespan as a human, typically up to 100 years and as much as 110.
Powers & Abilities
In their human forms, the Changelings also appear to be immune to the effect of sunlight just like Stalklings, thus making them the perfect spies for the Gumm-Gumms. Some of them, like Stricklander and Nomura, are accomplished warriors.
Because of their +2 Charisma bonus, the best classes for changelings are Bard, Rogue, Paladin, Wizard, and Sorcerer.
The short version is that a Changeling can shapeshift to a form that can produce sperm to impregnate someone, and can shapeshift to a form with a uterus and eggs to get pregnant, but a pregnant Changeling cannot shapechange to a form without a uterus without ending the pregnancy.
The Borg nanites are only able to adapt carbon-based lifeforms, which is why they were unable to assimilate species 8472. The changelings consist of a morphogenetic matrix making adaptation impossible because no single cell serves a single purpose the nanites wouldn't be able to adapt and maintain.
In Changeling: The Dreaming, Changelings as well as True Fae are weak to cold iron, in the mechanics of the game, cold iron does "aggravated" damage to Changelings and True Fae, meaning it cannot be healed with any supernatural means or accelerated healing powers.
Same applies to limbs. Under this system, changelings could regrow lost limbs or hair, but it puts significant metabolic strain to do it (e.g. healing surges, needing a large meal, etc.).
Changelings are amphibious creatures. They can breathe as easily in water (both salt and fresh) as they can in air. They can swim through water as easily as they can run on land.
While you are in the form of this persona, the related proficiency bonus is doubled for any ability check you make that uses that proficiency. Adaptive Body: You have advantage on saving throws against poisoned and you have resistance against poison damage.
Lightning: Changelings have a strange weakness that Dopplegangers do not--electricity. Any shock damage dealt to a Changeling can be lethal.
Changelings can look like anyone at any given time though they do have a true form. Their natural look is that of an asexual humanoid with ashen skin, light grey hair and milky white eyes. Their bodies tend to be long and slender, more so than elves but beyond they lack any distinctive features.
Meanwhile, the child changelings feed off of the human mothers' synovial fluid by suckling with their round, many-toothed mouths at the back of their necks. The changelings take their place in human homes as soon as they are formed, and feed off the mothers until they waste away.
Elves live the longest, with the Drow being the longest living of all the elves having topped 1000. No Drow who's lived over 1000 has died of old age or natural causes though, so their full lifespan is only speculation.
The Traveler is the patron of all those who welcome change, in body and in philosophy. Its worshipers include changelings, shifters, doppelgangers, and lycanthropes, who see it as the greatest of gods, but only doppelgangers and lycanthropes routinely revere it.
Due to their unique biology Changelings do not have active fertile cycles. Instead, a Changeling actually makes a conscious decision to begin a fertile cycle that lasts for two days, but repeats the cycle every fifteen days.
The D&D 65% Rule is a guideline suggesting player characters (PCs) should hit about 65% of the time against monsters with a Challenge Rating (CR) equal to their level, serving as a baseline for encounter balance, though many DMs find it overly simplistic and often ignore it due to the DMG's monster stats being inconsistent and its assumptions not always matching actual play. It comes from analyzing the Dungeon Master's Guide (DMG) monster stats, which show monster Armor Class (AC) often aligns with a ~65% hit chance for standard attacks, but this isn't always accurate for real monsters.
D&D by Tomatoes Strength is being able to crush a tomato. Dexterity is being able to dodge a tomato. Constitution is being able to eat a bad tomato. Intelligence is knowing a tomato is a fruit.
Rule 0 or rule zero in tabletop role-playing gaming is the unwritten but commonly understood rule that the game master can override published game rules for any reason.