The initial cast costs one black mana, and then with it on the board, you can pay another single black mana and discard a creature card to return a creature from your graveyard to your hand, thus making it a strong recursion tool
It was used it MTGs early years to play 3- and 4-MV cards ahead of time, but now the main application is in storm engines to generate enough mana to play a card like Ad Nauseam or Dark Petition
8 Little John, Resourceful Outlaw Although Little John costs six ink to play, this card can be shifted on top of another character of the same name for only four ink
Lotleth Troll is a lot of monster for the price and reminds me most of a mini Spirit Monger
Because of the presence of hand disruption your individual cards matter so much more in those matchups, meaning this card only becomes good when you cast it to win the game
(Another example of this is the afore-mentioned Ravenous Chupacabra) Do you really think that'll be it