Answer:
They are toothy nocturnal immortals.
Its days are numbered.
Once you know it exists, it no longer exists. What is it?
In the middle of night, I surround the gong. In the middle of sight, I end the song
Nothing specific, but more than a few. This many clustered, together will do.
It is something you will never see again.
Easy
Animal
Difficult
Food
Funny
Kids
Logic
What am I?