Strix are an owl-like avian native to Esper. Like other creatures of Esper, they have incorporated etherium into their physiology.
Its beak rends flesh and bone, exposing the tender marrow of dream. (Baleful Strix)
The scullers beneath Esper keep strixes as trained pets, and set them loose when a fare refuses to pay. (Tidehollow Strix)
After finding no sustenance on the edges of Grixis, it turned to the skies of Bant. (Parasitic Strix)