Five crime family decks, one per three color wedge, built on casualty, connive, blitz, shield counters and a pile of Citizens.
Sacrifice a creature with power N or greater as you cast a spell and copy that spell. The Grixis deck treats creatures as spell components, which is a strange and effective way to build a spellslinger deck.
Draw a card, discard a card, and get a +1/+1 counter if you discarded a nonland. Filtering and growth on the same trigger, and the Esper deck runs it on evasive creatures.
Cast a creature for its blitz cost and it gains haste, draws you a card when it dies, and gets sacrificed at end of turn. Fast value, and the Jund deck reduces the cost so you can chain several in a turn.
A permanent with a shield counter removes the counter instead of being destroyed or damaged. It makes the Bant deck threats far harder to answer than their stats suggest.
New Capenna is Magic's crime family plane, and each of the five decks takes one family and its wedge. The mechanics are unusually distinct for a Commander set: casualty, connive, blitz and shield counters all play differently from each other.
Alliance runs underneath the whole product as the trigger for creatures entering, which is why the token decks feel busier than their card counts suggest.
Casualty is the one worth understanding before you sit down. Sacrificing a creature to copy a spell sounds expensive until you notice that the copy resolves first and that token creatures count. In the Maestros deck, a two mana instant frequently becomes two instants and a dead token you were about to lose anyway.
Shield counters deserve a mention too. They read as a small protection effect and play like a much larger one, since the counter absorbs the first destroy effect or damage aimed at the permanent. In a format where most removal is one for one, that turns a single blocker into a two turn problem.
Maestros Massacre has the highest ceiling and the most rules questions. Riveteer Rampage is the most fun to play at a casual table.
Perrie, the Pulverizer · Kros, Defense Contractor
A Bant +1/+1 counter and shield counter deck led by Perrie, the Pulverizer, stack diverse counter types, swing for massive damage equal to the number of counter types, and protect your board with shield counters.
Kitt Kanto, Mayhem Diva
A Naya go-wide tokens deck from Streets of New Capenna. Kitt Kanto, Mayhem Diva makes Citizens and turns your creature count into a pile of combat pressure while goading enemy blockers out of the way.
Anhelo, the Painter · Parnesse, the Subtle Brush
A Grixis casualty and spell replication deck led by Anhelo, the Painter, sacrifice creatures to copy the first instant or sorcery you cast each turn, and win through doubled removal, card draw, and board wipes.
Kamiz, Obscura Oculus · Tivit, Seller of Secrets
An Esper connive and evasion deck led by Kamiz, Obscura Oculus, make one creature unblockable each attack, draw cards through connive, and steal opponents' resources with combat damage triggers.
Henzie "Toolbox" Torre · The Beamtown Bullies
A Jund blitz and ETB value deck led by Henzie 'Toolbox' Torre, cast creatures with blitz for free using a cost discount, trigger powerful enter-the-battlefield effects, and win through overwhelming creature-based value.