Retreat cost refers to the amount of energy cards needed to switch your active Pokmon with another one during the game
You cannot discard the things you draw so you need to have the things you want to bin in your hand already
Do Magic: The Gathering cards hold value
Archmages Charm is extremely pushed, a solid permission spell, a good way to build card advantage for hitting land drops, and a fantastic tool against Deaths Shadow, Wild Nacatl, Goblin Guide, Pyxis of Pandemonium, Champion of the Parish, Aether Vial, Delver of Secrets, Hardened Scales, Amulet of Vigor, Benthic Biomancer, Glistener Elf, Noble Hierarch, Viscera Seer, and sometimes even Hexdrinker (just to mention a few)
Today Darksteel Colossus has been supplanted by Blightsteel Colossus, but many Storm decks are eschewing the Tinker / Bot kill anyway
I really don't like these items that are single use though