I am the hidden land
Where man may not tread but wildlife can

Here a group in full did travel
By peak twilight, by horse and paddle

The group spoke sin and thus went in
To rule over all within

Where am I?

HINT 1

Man may not tread in this place but man is not the only species in this universe

HINT 2

This place is a place of great beauty and serenity

HINT 3

Man may only enter this place if invited in