I have a stiff shaft and my tip penetrates. I come with a quiver. What am I?

On a plateau of keys, when things go wrong, im probably the first key you try to leave. No need for control, alternatives and deleting things if this key works

Trains follow me both night and day, though I myself don’t move or stray.

Crisp, I sweeten your autumn days I grow soft when you show me warmth Cut me and you'll see my star Gift me with spice, and I'll satisfy you further

You found me where no thing should be, Too smooth, too dark, too perfectly. You stare at me, and I stare back too, Though I have no eyes to look at you. What am I?