Answer:
When you need me, you must find me. When you find me, you no longer need me. What am I?
What goes in the water black and comes out red?
A single syllable do I claim black was my most famous name; Fetal to mortals here below thousands have I slain in a single blow.
I can speak with my hard metal tongue. But I cannot breathe, for I have no lung. What am I?
By myself, I'm practically nothing. Worthless as a leader, but when I follow a group, their strength increases tenfold. What am I?
The answer I give is yes, but what I mean is no. What was the question?