If boards are roughly equal, Liliana's +1 ability will warp the game around efforts to remove her, a task made difficult by a steady stream of 2/2 Zombie chump blockers and extra cards being poured into the defending players' hand
Its also just difficult to interact with it completely dodges creature removal, and you cant Counterspell the ninjutsu ability, so the very moment you decide not to block a creature, Kaito, Bane of Nightmares hits the table, and its sticking around at least long enough to use a loyalty ability and pass the turn
That means we want Wizards to come out and announce this is a rule now, because it seems odd to say otherwise for no real reason
Overall, this tiny bug is the card I was most excited about from the entirity of The Brothers War and the surrounding releases
Mana-dork-oriented decks often suffer in the late game when they start drawing fragile little Creatures instead of actual threats, but this leyline's activated ability can turn all your extra mana into +1/+1 counters for your whole board