There are sometimes exceptions, but generally speaking, a card is classified as high-end by us starting at this value
You must do so even if it requires targets and the only legal targets are ones that you really don't want to target
Effects might see your cards returning to your hand instead of the discard pile when banished, or locking down opposing characters for a turn - making it unable for them to challenge or quest
Its ability looks pretty insignificant at first but combined with certain cards, it can help you produce infinite mana, buff your creatures with a gazillion counters and draw at the same time, or even have infinite turns
Edgar Markov is by far the best Vampire to lead your armies, having an eminence ability that lets you pump out Vampire tokens even while hes in the Command Zone, an ability which is arguably too powerful