I sound like I'm near where a staircase once went,
Or guarding a place that's impossible to reach.
But I'm really a creature that you've never seen:
My home is remote as it's possible to be.
Though I really exist, and so does my home!
Family's a mystery, I'm so small and different.
Find the two-word answer.
The answer is two words. Each verse refers to a different possible meaning of those two words. The "sound like" does not refer to homophones; the same two words can be interpreted in different ways.