As I explained last week, Vision Design created a typal mechanic called fellowship as the other glue to hold together the set. Set Design decided to pull fellowship (which I'll get into next week) and in its place give each archetype its own mechanical identity. Some archetypes would get a keyword/ability word, while others just got mechanical throughlines. Each would get a small amount (around eight) of typal rewards, skewing higher in rarity. I'll walk through each archetype in order and explain its mechanical identity.

Birds (White-Blue)
Birds are one of two animals in the set that all come with the same keyword—flying (the other being Bats, which I'll get to in a minute). To add a little flavor and keep from having two archetypes all about flying, the Set Design team decided it would be interesting to have many of the Birds mechanically care about non-fliers, creating this synergy where the deck wants a mix of fliers and non-fliers. Being white-blue, it has the normal amount of control elements to help you protect your fliers, which serve as your win condition.

Rats (Blue-Black)
Rats have access to several elements that will slow down your opponent. It has creature kill, counterspells, discard, and strong blockers that will allow you to fill up your graveyard as you're stalling out your opponent. There are then a number of Rats that care about having seven or more cards in your graveyard, upgrading them in the mid- to late game and helping you win.

Lizards (Black-Red)
Lizards are one of the more aggressive decks. Its main strategy is two-fold. First, it has a lot of cards that enhance its creatures in aggressive ways, encouraging you to attack. It then has several effects that deal damage directly to the opponent, so you can plink away at their life total from afar as you're constantly attacking them. Lizards don't have a named mechanic that runs through the archetype, but they do tend to reward you for your opponents losing life.

Raccoons (Red-Green)
Raccoons are a midrange ramp deck that wants to get out a lot of larger creatures. It has cards that grant a bonus if you control a creature with power 4 or more. It also makes use of a brand-new mechanic called expend. Here's the reminder text for expend 4:
(You expend 4 as you spend your fourth total mana to cast spells during a turn.)
Expend rewards you for playing big spells but can also reward you for choosing to play multiple small spells on the same turn.

Rabbits (White-Green)
Rabbits like making a lot of Rabbits. It's the creature that has the most cards that create tokens, and it has the most cards that make multiple tokens. You'll play a lot of Rabbits, which will allow you to create a lot of Rabbit tokens, which will let you build up a giant army that you can then swarm with to defeat your opponent. It has a lot of spells that either reward you for having many creatures or buff your creatures to allow you to attack.

Bats (White-Black)
Bats, like Birds, can fly, but we wanted to give them a different feel. We leaned into Bats caring about life, as white is top in life gain and black is best at spending life as a cost. Bats play more like a bleeder deck where you slow down your opponent with good blockers and defensive spells, using life gain to buy yourself time and life loss to dig into your opponent and finish them off with your fliers.

Otters (Blue-Red)
Otters are the wizards of Bloomburrow. They care about instants and sorceries and have a lot of cards that reward you for casting them. This archetype plays less creatures and more spells, especially ones that help you control the battlefield, and has more of a tempo-oriented play style.

Squirrels (Black-Green)
Squirrels are another creature type to get a new keyword (technically a keyword action) called forage. Here's its reminder text:
(To forage, exile three cards from your graveyard or sacrifice a Food. If a creature with a finality counter on it would die, exile it instead.)
Forage combines the Squirrels' focus on two things: the graveyard and Food. Squirrels have a bunch of ways to get cards in your graveyard and ways, including forage, to use your graveyard as a resource. The archetype also is good at producing and using Food tokens. That, combined with removal and big creatures, helps lead Squirrels to victory.

Mice (White-Red)
Mice are the most aggressive archetype. They like attacking, so they skew toward low-mana value creatures. They also have a new mechanic called valiant. It is an ability word with the following text: "Whenever CARDNAME becomes the target of a spell or ability you control for the first time each turn." It's a variant on the heroic mechanic from the original Theros block, but it's triggered by spells and abilities and only triggers once per turn. Valiant works well with combat-enhancing spells and Equipment.

Frogs (Blue-Green)
Frogs like to jump, so it takes advantage of effects that either bounce it (returning it to the hand) or flickering it (putting it in exile and then bringing it back). Frogs have a lot of enters-the-battlefield effects and triggered abilities that care when creatures enter or leave the battlefield. The synergy grows as you get more permanents on the battlefield, adding extra value to strengthen your late game.