You can't choose multiple creature types, such as "Vampire Knight." Card types such as artifact can't be chosen, nor can subtypes that aren't creature types, such as Jace, Vehicle, or Treasure
To be able to use that move, you have to have a specific amount of energy attached to that card
(Naturally, this deck is fictional, but decks dedicated entirely to burning the opponent are very real)
Ninjutsu is a powerful ability that lets players swap out unblocked attacking creatures for a creature with ninjutsu
Maybe if the table is down to you and one opponent and it makes sense for that one player to cause them to discard their hand and draw seven new cards
I've also had Golgari aggro decks that push tempo and leverage a fast start using removal and combat tricks to push damage and close games early