Not only does it help you with attacking, it also helps with defense, being a great blocker with reach
Liliana may be hiding an axe behind her back in the art (hence the "chopping" pun on last-minute shopping), but she can be easily bribed with a gift
If your starting deck follows that rule, then the creature can serve as your chosen companion." The Wiki goes on to explain how you can only have one companion in a game, it starts outside the game, and counts towards your sideboard size (i.e., in Constructed play it is one of the fifteen cards in your sideboard)
Because it isn't a planeswalker itself, it won't enter the battlefield with any loyalty counters, but it also won't die because due to not having any
Much like Terra has a double-face card, Kefka gets the same treatment, with Kefka, Court Mage transforming into Kefka, Ruler of Ruin, just like in the games