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Every 50th kill of this enemy drops Vulture Banner.where they come from
Daylight and desert sand is the usual pairing, and nothing summons them. The rule that catches people is the second one. Any exposed sand block anywhere in the world can have one perched on it, so a sand ledge in a forest or a patch above a cave mouth is enough. A roosting vulture sits completely still and ignores you until you walk close or hit it, which is why they so often end up behind you.
the dive has a windup
Once awake, it climbs until it is more or less overhead, hangs there for about a second, then drops. That pause is the whole fight. Step to one side while it lines the dive up and it plows into the ground, leaving you a clear window while it climbs back. Trading hits on the way down is where the damage comes from. There is also no losing one. After it has picked you it follows until one of you is dead.
the cheap answer
They cannot follow you under the surface of water. An oasis pool works, and so does any hole you flood yourself. For a character still in starter gear that is a complete answer to a bad desert.