Its almost always used as a secondary creature type in conjunction with a more popular one (vampire horror, for example), though there are a few stand-alone horrors
Common Uncommon Rare Super Rare Legendary Enchanted Take a look at the symbol at the bottom of these three character cards from The First Chapter
Once again, look at the difference between the two fonts
The mystery cards are usually 25 random common cards and 1 rare card, offering very little value
Lands Since we're a 3C deck, most of our land slots are devoted to mana fixing, but we have some fun Counter stuff too like Llanowar Reborn, and manlands like Inkmoth Nexus
They can be any type of card, from stellar legendary creatures to the greatest card draw spells to the most valuable ramp spells