Is it sea kelp
I live with first ones ,they use me well! For the others I am hell! For the third ones I am useless,you can't touch me but you can see me! I am always there within you! Seek for me and and I'm right there! What am I?
I live and thrive in the winter as I grow down and sharpen but you’ll never see me in the summer because I’ll die in warmth. What am I?