In Pathfinder 1st edition, an Aasimar descended from such a Celestial was known as an Idyllkin Aasimar.
Idyllkin often possess bestial qualities such as dragon scales, fish scales, fur, manes, or talons. Slit pupils, pronounced canines, and furry ears are all common indicators of an aasimar’s agathion background. Just as agathions take on different traits depending on their animal aspect, so too do idyllkin. Descendants of avorals often possess feathery hair and enjoy wide-open areas such as plains, while the progeny of leonals are aggressive and often have sharp, clawlike fingernails. Many idyllkin, regardless of their animal aspect, feel called to walk the path of the druid, and idyllkin are among the most likely aasimars to become such protectors of nature.
Agathion= Guardinal btw.
Before the alignment restriction was removed for Monks, Idyllkin Monks were something of an exception to this rule. They could be Neutral Good or Neutral and still be a Monk because of the half-feat Enlightened Warrior.
Nice comparison between Pathfinder Idyllkin and the playtest Ardling, likewise pointing out 2e Guardinals correspond to Pathfinder Agathions. (Not to be confused with 2e Agathinon, with an extra -n-, who are Celestial military telepathic shapechangers, whose true form looks an Elf with glowing eyes.) "Agathos" is the Greek word meaning "good".
For the rest of this long post, I am musing out loud.
In brief. As a core option, the Ardling does better to have the option of a human head to appeal to Aasimar fans, as well as the option of an animal head to appeal to Tabaxi fans.
For the sake of the D&D 5e game as a whole, adding Ardling to core seems like a strong strategy. It has traditional D&D cachet, and also functions as a go-to place for the many different kinds of humanimal character concepts.
That said. I have mixed feelings about how I myself would play an Ardling character. I would want this "core" angelic option to be able to have a human head.
I know, it is trivially easy to have a character who is Mixed-Species, thus has a human head while using Ardling mechanics. My feelings are more about the angelic flavor of the Ardling. For various reasons, the Ardling does well to include the possibility of a human head.
I like the archetype of the human-appearing angel, that one finds among the traditional D&D Aasimar. If the Ardling species displaced the Aasimar species from out of the core twelve options, I would miss it.
I would rather see a core Ardling absorb the Aasimar traits, in the sense the Ardling too can have a human head.
Compare the playtest Tiefling species that newly can come from any Fiend plane, including demonish Abyss and yugolothish Hades, in addition to the Infernal devilish Hells.
The 2014 Tiefling only inherited the Hells. But the playtest makes other Lower Planes possible too, including LE Hells, E Hades, and CE Abyss.
(By the way, Hades is the Greek name for the Greek concept that is now moreorless the same thing as 5e Shadowfell, namely the underworld. It is unhelpful to call the Astral Evil "Hades", when it is more Neutral like Shadowfell. Maybe rename the Astral dominion as "Tartaros" instead of Hades. Tartaros is a place of punishment, like Hell, and is more suitable for the name of a lower Evil plane.)
As a counterpart to the Tiefling, I hope the Ardling also becomes able to come from any of the Upper Planes. There should be Ardling who come from LG Mount Celestia, G Elysium, and CG Arborea, as well as less visited planes of Good.
Any Ardlings from Mount Celestia or Arborea are likely to have human heads.
But even among the G (Good) Guardinals, it is worth pointing out. The Guardinals of the plane of G Elysium are typically human looking. It is the neighboring plane of GCG (Good by Chaotic Good) Beastlands that has the Guardinals who are typically humanimal looking.
Even an Ardling who descends from Guardinals should include family members with human heads.
In earlier editions, "Planetouched" typically meant a Human who a plane transforms. A Genasi is "touched" by one of the Elemental planes, a Tiefling is transformed by a Fiend plane, and the Aasimar is transformed by any of the Celestial planes. There are Aasimar who inherit LG Aasimon traits, from Solar, Deva and others. But there are also other Aasimar who inherit NG Guardinal traits. Likewise, there are Aasimar who inherit the 2e CG Eladrin traits. There are even Aasimar who inherit traits from other Celestial creatures such as Couatl.
In this sense, the playtest Ardling is mainly a specific kind of Aasimar, the kind who descend from a specific kind of Guardinal.
But even this kind of Aasimar who descends from Guardinals should include members who have human heads. Because even some of the Guardinals who are native to the Beastlands are humanlike, even tho most are humanimallike.
It may even be, the Ardling is intentionally a new name to replace the name Aasimar − heh − in an attempt to avoid the distracting misreading "Assy-mar". But here I would prefer a new spelling for "Awsimar" to intentionally invite the misreading "Awesomer".
In any case, as a neologism for Aasimar, the Ardling should include Celestial members that have human heads, in order to continue the D&D traditions about humanlike Aasimar.
There are diverse traditions, but earlier editions typically understood the "ancestry" of an Aasimar to be a magical transformation of a Human by the influence of a creature in the Celestial planes. The Aasimar transmits a supernatural inheritance. While the magic does alter the Aasimar physically, it is a magical legacy rather than a sexually reproductive biological one.
Compare 2e, 3e, 4e, and 5e Tiefling. The 2014 Players Handbook describes the Tiefling as a Human that hellish magic transmogrifies. "Tieflings are derived from human bloodlines, and in the broadest possible sense, they still look human. However, their infernal heritage has left a clear imprint on their appearance." The Tiefling is a variant Human, or more exactly, a "planetouched" Human.
The playtest reverses this. According to the playtest, "Tieflings are either born in the Lower Planes or have one or more fiendish ancestors who originated there. A Tiefling is linked by blood to a Devil, a Demon, a Yugoloth, or some other Fiend." Notice, the Tiefling is now an extraplanar creature, a native of certain Evil dominions in the Astral Sea. In earlier traditions, the Tiefling is a Human who has been altered by the influence of a Fiend. But now, it is the other way around. The Tiefling is a Fiend, who has been altered by the influence of humanity.
I prefer the playtest. To make the Tiefling an actual Fiend makes the species a more interesting and distinctive choice for a character concept. I hope the Tiefling creature type is "Humanoid Fiend", or at least, "Humanoid or Fiend".
Helpfully, the playtest returns to the tradition that the Tiefling might represent any of the Fiend planes, not just the Hells, but the Abyss and the
Hades Tartaros too, and some of the less visited Fiend planes, like ECE Carceri or LLE Acheron. Tiefling are indigenous to any of the variegated Evil dominions in the Astral Sea. While it is still possible for a Tiefling to be a transformed Human, most Tieflings that one encounters in the Material plane are immigrants from the Astral Sea. Tiefling are extraplanar Fiends.
The playtest juxtaposes the Ardling and the Tiefling. They mirror each other. Where the Tiefling are from the Lower (namely the Evil Fiend) dominions, the Ardling are from the Upper (namely the Good Celestial) dominions.
Both the playtest Ardling and the playtest Tiefling are otherworldly Astral beings, namely the Celestial and the Fiend creature types respectively. These species are made out of Astral thought stuff. These are otherworldly immaterial creatures, whose forms transfigured under the influence of humanity.
Unfortunately, where the playtest Tiefling broadly now allows for the various planar Fiend concepts, the playtest Ardling is now overly specific, about only one kind of Celestial concept: an animal-headed anthropomorph. According to the playtest, "Celestial animals roam the Beastlands, a [GCG] plane of untamed beauty and wild nature. Many of those otherworldly animals serve the Beast Lords, and in the early days of the multiverse, some of the animals evolved into bipedal forms. Among their number are Ardlings, people with beastlike heads, keen senses, and an innate connection to Divine magic." In this case, the Ardling is specifically, a kind of Celestial bipedal animal that has an animal head. This is too narrow for the wider concept of Upper Planes. The Ardling is currently unable to represent the various Celestial character concepts who are the counterparts to the various Tiefling concepts.
As a core species, Ardling needs to include options that are human-headed like Aasimar.
Despite the Aasimar being behind a paywall, the 2022 DnDBeyond stats show them to be as popular as the 2014 core species, comparable to the popularity of the Gnome that is easily accessible without a paywall. There is a strong demand among D&D players for the Aasimar species to be core.
Either, the Ardling allows for a human-head to appeal to Aasimar fans, or the Aasimar needs to also be a core option alongside the Ardling core option. But why have two core Celestials? The competition for the small design space available for "core species" that will represent the tone of all D&D from this point on. It is more elegant to have one Celestial core species that can accommodate the need for both the fans of human-headed and the fans of animal-headed.
It is a needle to thread. On the one hand, the Ardling needs to have a human head to appeal more to Aasimar fans. On the other hand, it needs to be more overtly humanimal with an animal head, to appeal to humanimal fans.
Tabaxi is the "cat girl" species, or rather the "cat kid" species, including female, male, and others. Tabaxi too is popular. Altho it doesnt achieve the stats of the top twelve species, it is behind a paywall, and is thirteenth in popularity. Likely, the Tabaxi would prove more popular if it is a core species in the 2024 Players Handbook. So if the Ardling as a core species is to satisfy Tabaxi fans, it must feature prominently the kind of Ardling that is a cute Cat Kid.
This is the needle to thread, how to present the Ardling in a way that is either a Celestial human Aasimar, or a "furry" humanimal Tabaxi. Moreover, have this humanness versus furry-ness to a degree that satisfies both fans.
The flavor of Ardling needs to find a way to be both, despite being conflictive against each other.
