Angeon which travel to the Human Realm can be Collared. Collaring is done through the use of a Collar, which can be purchased in the Collar Shop.
Once you have one or more Collars, you can look on the Human Realm's "visitors" page on the EvoCrit site to see which Angeon are currently visiting. This will allow you to select a Collar and an Angeon, and then see if the Collaring was successful. The available Angeon are randomized every week, and 1-3 Angeon can visit the Human Realm at a time. If an Angeon is not Collared by the time the week is up, they will leave and may be replaced by another Angeon.
Angeon on the Human Realm visitors page will show a randomly-generated description, which may list their element, base species, important traits, and more. Not all of these pieces of information will be available for all Angeon at all times.
Once an Angeon is Collared, they will be added to your EvoCrit account to be certed. Their appearance will be determined at this time, as well as the rest of their traits. The Collar in their art will match the Collar that was used on them.