If a creature in combat has first strike or double strike, you can activate the library ninjutsu ability during the first-strike combat damage step
The so-called Nic Fit decks go a step further and actually take advantage of Cabal Therapys ability to let you sacrifice creatures
You can take their turn, get all their creatures tapped, spend their removal, tap all of their lands, and otherwise mess with them to leave the way open for your win
Besides those you can always look for cards that want you to sacrifice lots of creatures
Oftentimes, there will be dozens of creatures, artifacts, and enchantments on the battlefield
Her exact role as the Hand of Erebos isnt clear, but given her noble stature and color identity it seems likely shes a sort of peacekeeper in that strange star-specked land, watching over the common shades