It was Abraham's Earth Feather which I sought.
Dear Father, -- gender
I write to you today from beneath the shadow of a great black cherry tree. -- color reference & poison magic reference (the rotten leaves of the black cherry tree are extremely poisonous to horses)
It's raining lightly, but I am sheltered beneath its leaves. -- he's described as protective
I suspect that its roots sprawl far beneath the earth, but things aren't always what they seem, are they? -- he has a large family & he looks like a unicorn, but he's of mixed blood
Kindest regards to you and your many children. -- the name 'Abraham' means 'father of a multitude' in Hebrew.
Sincerely,
Your most devout follower.