Grist, the Hunger Tide is an insect! What does that mean?
Apparently, it means that Grist can be your Commander, which is pretty wonky. Along with Dakkon, this also marks another innovation to the way we approach loyalty counters on planeswalkers. Let's first evaluate Grist's power level at face value for 60 card formats, and then dive deeper into the weird interactions and whether or not there is enough support to do busted things in Commander.
The +1 ability is, at worst, simply create a 1/1 token and mill a card. This is actually not bad for a three mana planeswalker, as one of the benchmarks for successful planeswalkers is simply the ability to come down early and defend themselves. The bar is much lower for a 3-cmc planeswalker than a 4-cmc planeswalker as well. It's worth noting that if you're just running 4 copies of Grist as your only Insects (in a 60 card format), that still gives you a 5% chance of a bonus activation each time even without any library manipulation.
The -2 ability is not bad either, especially since it can target planeswalkers. The combination of the first two abilities lets Grist win a head to head fight against most other planeswalkers, and will often but your opponent in a bad spot if they're just trying to stick an important creature after you dropped Grist early.
Grist's ultimate is extremely easy to achieve in terms of loyalty, but it will take some time before it can close out the game (aside from potential combo applications). Grist is nice enough to help us out in getting it filled the fair way.
OK, so it seems like we have a fairly powerful set of abilities. But what can we make of the fact that Grist is a 1/1 insect while not on the battlefield? For starters, it means we can count him as a creature for cards like Collected Company or Unearth. Grist seems like an interesting "creature" to either cheat into play or use recursion on, since it can function as either a card advantage engine or a key piece of interaction.
There's enough going on here that it seems like Grist might be a consideration to play in formats like Modern! Now let's dive into Commander. For starters, let's see how many "good" insect cards there are.
1 Ant Queen 1 Bane of the Living 1 Brain Maggot 1 Caustic Caterpillar 1 Caustic Wasps 1 Crash of Rhino Beetles 1 Deadbridge Goliath 1 Decimator Beetle 1 Devouring Swarm 1 Distended Mindbender 1 Endless Cockroaches 1 Giant Adephage 1 Gleancrawler 1 Grave-Shell Scarab 1 Hex Parasite 1 Hornet Nest 1 Hornet Queen 1 Living Hive 1 Mazirek, Kraul Death Priest 1 Mortician Beetle 1 Moldgraf Monstrosity 1 Nantuko Calmer 1 Nantuko Cultivator 1 Nantuko Elder 1 Nantuko Husk 1 Nantuko Mentor 1 Nantuko Shade 1 Nantuko Shaman 1 Nantuko Vigilante 1 Necropede 1 Nullmage Advocate 1 Phantom Nantuko 1 Phyrexian Swarmlord 1 Scute Mob 1 Scute Swarm 1 Symbiotic Beast 1 Thriss, Nantuko Primus 1 Vorapede 1 Wirewood Symbiote 1 Xantid Swarm
That's a bigger list than we thought! Not all of these are slam dunks, but there's plenty to work with here. Not to mention all of the decent changelings (Chameleon Colossus, Cairn Wanderer, Graveshifter…) If we are able to run 40 insects in our Commander deck, well, the math is pretty easy…Grist's +1 ability has a 40% chance to continue each time! (Well, there are actually 99 cards in our maindeck but whatever). Maybe we could run a full 60 insects? It seems pretty easy to ultimate Grist for the win after just a few activations.
Conspiracy is an obvious slam dunk if you don't want to go the all insect route. It's too bad we won't be able to use Arcane Adaptation in Commander, but maybe that type of combo has applications in other formats.
Ooh, here's something cool! These four seldom-used black cards let us stack the top of our deck with any insects that we've turned face up so far. These cantrips suddenly just put a ton of 1/1 insect tokens into play and get our Grist to an absurdly high number of loyalty.
This exercise turned out to be more interesting than we thought when we first read the spoiler! Whether you focus on the weird insect-ness of the card or not, Grist looks like it could be the real deal!