I am filled with trash but I am not a landfill. I am filled with fish but I am not a sea. I am filled with colours but I am not a rainbow. What am I?

Echoes sing within, A hidden mouth of the earth, Secrets carved in stone.

A mythical creature prize for its horn and so elusive its evades us all.

I borrow my glow and spend it each night, A thief of the sun dressed softly in white. I pull at the seas without touching their skin, I wax and I wane as old clocks begin. Named yet unnamed, I vanish by noon. Look up when it’s dark, and you’ll know me soon.

I'm born of orchid, yet lack floral grace, A culinary friend, in time and space. Though plain I seem, my essence is grand, Lending depth to flavors, across the land. What am I?