Each one solves fundamental problems that the majority of decks face while providing exceptional value across multiple archetypes
Normally, you pay a bunch of life into them and get the cards at your end step
This is the first Pokemon region designed to be an island, and this can be seen in every facet of its design
Kumena is here for card advantage versus control, to stabilize aggro matchups due to his 2/4 body, to pump your folks to overcome huge boards sitting here and not daring to attack you or just to finish players with his evasive ability
Since Sefris gives us the rare opportunity to reanimate things at instant speed (any time we can get the last venture trigger in), we can even use these hatebombs reactively to blow out our opponents like reanimating Sunblast Angel in response to an attack, or Avacyn, Angel of Hope in response to Wrath of God
The problem is they present a certain awkwardness by doing nearly nothing without a Commander