Different lights make me stranger, for each one my size will change. What am I?

Soft and warm for your feet, we come in pairs, but don't separate in heat. We slide right on, easy peasy; we come right off, just as easy.

Of stegosaurus, of armored knight, of dinner table by candlelight. Remove my first letter, you'll find me tardy. All scrambled up I fall from wilted head. Both remove the first then scrambled: I'm that which is spun sans spool or thread.

Knick-knacks found in stores of thrift Souvenirs from time away Trinkets given as a gift Useless but to decorate

I’m small and dark, yet ground for bite, often beside my friend in white.