Aven are a species of humanoid birds native to several planes in Magic: The Gathering. They are predominantly associated with the plane of Dominaria, but have also been seen on Amonkhet, Tarkir, and Alara.
The common Dominarian aven resembles a humanoid raptor, similar to the aarakocra from Dungeons & Dragons. A sub-species which resembles a humanoid owl is also native to Dominaria; whilst both aven can and do make skilled wizards, the owl-like aven are less militant than their raptorial cousins, are just as likely to be fighters or gishes. The race suffered greatly when the Mirari poured their magic over Dominaria, mutating them considerable; owl aven transformed into the larger and more monstrous-looking Crookclaws, whilst the hawk avens devolved and became giant eagles with human-like intelligence.
Dominaria is also home to Elens, a hulking race of wingless, featherless mutant aven most likely created by the Order in Otaria to serve as expendable pawns, the Kathari, a race of scavenging vulture-people native to Grixis, and the Raypen, which are sort of the halfling equivalent of common Aven.
Tarkirian aven are much more feral-looking, as their arms and wings are a combined limb structure, instead of having seperate arms and wings. They come in vulture-like, raven-like, crane-like, and hawk-like subraces.
The Aven of Amonkhet are much more human-looking; taking inspiration from the obvious Egyptian theme of the plane, they resemble humans with bird heads and wings coming out of their shoulders. They come in Ibis-headed (dedicated to the God of Knowledge, who as not!Thoth looks just like them) and Hawk-headed (dedicated to the God of Solidarity, who ironically is a catgirl goddess) subraces.
PC Stats (5e)
The Amonkhetian Avens were made into a playable race for Dungeons & Dragons 5th Edition with the release of the "Plane Shift: Amonkhet" web expansion. They receive +2 Dexterity, are Medium sized, have a base walking speed of 25 feet, and have a flying speed of 30 feet, although they can't fly if wearing medium or heavy armor, or if they're encumbered. Ibis-headed Aven get +1 Intelligence and can add half their proficiency bonus (rounded down) when making Int checks for non-proficient skills. Hawk-headed aven get +2 Wisdom (making them one of a very small number of races with +4 to ability points), free proficiency in Perception, and can ignore the long range penalty when making ranged attacks.
Dominarian Avens likewise joined their brethren in the pages of Planeshift, but are identical to the hawk-headed Amonkhetian Aven above in terms of their stats.