The Fate Collab is now in full swing and while Rare Egg Machine portion is lackluster (full Review can be found HERE), the Farmable Servant, Assassin is an incredibly valuable card and should be acquired by most players.
The reason for this is that he functions as both a double Row generator along with possessing a special Button nuke.
Servant, Assassin can be acquired through either 5 Rainbow Event Medals or by heavily grinding the Fate event dungeon. Either way, one can find Servant, Assassin in the Monster Exchange Event tab for the duration of the Fate event.
—video coming soon–