These will transform after you fulfill some kind of condition on the card, usually either an activated ability (i.e., paying to exile Terra, Magical Adept) or triggered ability (i.e., having six permanents in the yard for Exdeath, Void Warlock at end of turn)
Locations are ways of producing passive amounts of Lore for you (as a reminder, the goal of Lorcana is to be the first to get twenty Lore points), and can also provide benefits to characters located here
Make them sacrifice creatures
This is the high-end option designed for collectors who want the rarest treasure from the Spirit World
Deaths Shadow is mostly an outdated Constructed card that doesnt really have a home anymore
Finally, the biggest part about building a custom deck is to truly customize it