These were the immutable facts about this creature I was working with:
I was instantly relieved to see it was such a low CR. Was nice to work within the confines of a simpler stat block.
There is a notable lack of both weak and non-good aligned Celestials within the existing D&D canon. Which makes sense, divine things are both powerful and good, typically. I wanted to challenge myself and make something interesting with this prompt, so my aim was to make a creature in a similar niche to goblins or kobolds. A grimy little villain encountered in packs at low levels. I think it's an interesting divergence from what Celestials ordinarily are in D&D.
A worm does not know the difference between a human and an angel. To a worm, meat is meat.
What these little detrivores do not understand as they bite and swallow the holy flesh of an angelic corpse, is that something so lowly was never meant to devour something so supreme. Soon, a worm will find itself transformed by what it has ingested. Ordained. Canonized. Its body contorts in size and shape as it digests divine DNA. It grows a brain to comprehend the holy, a heart to to feel devotion, and hands to clasp in prayer. The diminutitive worm becomes the Holy Scrounge.
The Scrounge, though a celestial, remains a scavenger, but elevation to divinity has broadened its taste from rotting meat and soil to other, greater treasures.
Scrounges lead lives in pursuit of all things magical and divine. They usually travel in small bands, led by a dim internal insight as to the location of precious holy magic. They make pilgrimages to all kinds of holy places, abandoned and still in use, particularly attracted by the magic items these places hold. They look upon these places with a great deal of reverence, and admire the beauty and power of all kinds of arcane trinkets.
Of course, there is a reason why worms are not ordinarily ordained with Celestial power. It is the same reason not every man can be made a saint. Ascension does not change a creature's essential nature.
Although Scrounges internalise the mortality of whichever deity the Celestial they dined upon was devoted to, they constantly struggle to muster the will to adhere to that god's ethics. While Scrounges will often pay proverbial lipservice to their god, performing banal rituals in their honour, or cladding themselves in their colours, the moment an opportunity for food or treasure arises, religiosity loses its priority. After a moment's painful deliberation, Scrounge will nearly always choose to trick, steal and kill if there's a profit to be made.
After a Scrounge has succumbed to temptation and committed an act in defiance of its god, it will without fail throw itself to the ground and weep for forgiveness. The natural sense of morality conferred from its ascension is not strong enough to stop it from sinning, merely enough to fill it with a terrible guilt when it inevitably does. Though its transformation has let the Scrounge understand right from wrong, its will to act ethically remains that of a worm.
As a result of this perpetual guilt, Scrounge are highly irritable and neurotic creatures. They are perpetually bothered, suspicious and quick to assume ill intent. Scrounge frequently become convinced others covet their plundered treasures, leading to packs of Scrounge constantly bickering amongst themselves. Scrounge are particularly wary of Humanoids and other intelligent non-Celestials, quick to assume the worst intention. They often take violent prophylactic measures against outsiders to prevent future slights they delusionally believe to be inevitable.
Bands of Scrounge typically keep their distance from Humanoid settlements, not able to stay long before trouble starts. Churches and monastaries sometimes show kindness and open their doors to travelling bands of Scrounge loyal to their god, but rarely does this arrangement last. A magic mace on display in a glass case is simply too enticing to resist.
At night, in the throws of guilt induced internal torment, many Scrounge lay awake and lament the fundamental contradiction of their being. To know what it is to sin and to be too weak to resist... it's enough to make one miss being a worm.
If angel corpses and religious angst was a bit too dark for your taste, my next roll produced a much goofier monster.