This is a downside if you're removing +1/+1 counters or similar, but removing a lore counter from a saga is all upside, keeping it in play for another turn and rebuying your earlier saga abilities
As for card advantage, look no further than Glimpse of Nature and Beast Whisperer and other cards that make super cheap creatures cantrip
We also wanted Volrath, the main villain, to sneak aboard the ship later in the story (more on that in two weeks), so we liked the idea of a traitorous character who helps out the crew only because there's something in it for himthe rescue of his daughter (named Takara)
I will concede that creature pump feels odd in black, but it's not entirely foreign ( Dark Favor , Looming Shade ) and when you consider Brine Shaman , Wicked Reward and Armor Thrull , it's at least arguable when you sacrifice a creature