Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to a creature may become lethal if Eye of Nidhogg becomes attached to it or unattached from it during that turn
Many cards name or exclude what they can target, so Acidic Slime does not hit planeswalkers, whereas Jhoira's Familiar, Airbending Lesson, Disruptor of Currents, Leyline of the Guildpact, and Bramblecrush can apply to planeswalkers
As part of the game's most recent reveal stream, Magic: The Gathering Strixhaven mechanics were on full display, and an exciting new one in the form of Learn and Lesson cards looks poised to inform deckbuilding decisions in interesting ways
I find it also puts you in the light of an ally for a while since you "assisted" in removing a threat or two
It can take out a player on its own, but landing even one hit on an opponent means they'll have Poison counters
It threatens damage quickly in a multiplayer game, but thats all it does