They were introduced in Series 3, the first series to be released outside of Japan
We all have cards we want to flash back, and getting additional value from cards you played a long time ago is great
Heres an example of a typical Trinity deck, to show you what decks generally tend to look like: Getting Started with Trinity619551 635 KB As you can see, every card is a 1-of, apart from Tour Guide from the Underworld, which is our Trinity, which costs 1 Point
Because it isn't a creature, it isn't a flashback spell, and it isn't even an instant or sorcery, Claustrophobia can be a bit out of place
It can also allow its host to see the dead
Draw Black offers some of the best draw options in the game, often at the cost of life