We're four cycles in now and Peter Sylvestre has been listening to our horror stories and calming our nerves like the loyal confidant he is since the beginning of Dunwich. I honestly don't know how he does it. It's been a while since anyone's written about him, so I thought I'd take a moment and just list out all the investigators that can take him, and explain which ones he fits best with.
Carolyn Fern - Pete is a popular choice in Carolyn decks. While his passive +1 boost isn't used at all, and while Carolyn has a whopping 9 Sanity, his ability to heal 1 horror per turn often makes him a pseudo Lone Wolf. I personally think you're better off running Alice Luxley or Dr. Milan Christopher, but Pete, especially when combined with Forbidden Knowledge, is a tried and true way to afford all that Dynamite. Carolyn also likes his upgraded version, which helps her lean into her Mystic side a bit more.
Zoey Samaras - Pete is sometimes seen as a one or even two of in Zoey decks, but it's not common. The +1 isn't particularly useful for her, but Zoey has a tendency to fight several monsters at once, and Pete can help soak up the horror from such attacks. Still, it's hard to justify him over Beat Cop or Guard Dog, and her limited five off class slots are often better suited to make up for her low (Drawn to the Flame, "Look what I found!", or even Rite of Seeking). Plus, with her 4 she takes horror much less often than many Guardians that would literally kill to have access to Pete (I'm looking at you Mr. Banks).
Minh Thi Phan - Peter is rarely seen in Minh decks. This is another investigator who has little use for the +1 and whose lessens the need for horror soaking. Seekers are also generally spoiled for choice when it comes to allies (we got Dr. Milan Christopher, Mr. "Rook", and even Laboratory Assistant, all of whom tend to help enable combos and synergies that Seekers just love so much).
Rex Murphy - Ah, finally someone who can actually enjoy the +1! Still, those five off class slots are precious. Rex also has a whopping 9 Sanity, and like Minh is spoiled for choice ally-wise. As a result he rarely sees play in Rex decks.
Finn Edwards - Might as well be an auto-include for Finn. The +1 is put to amazing use with Finn's free evade, but on top of that, Pete helps make up for Finn's frankly pathetic 1. Yes, Finn only has five slots for Survivor/Seeker cards total, but two of them will always be Peter Sylvestre. You will run two and you will like it. (Okay fine yes you could also run Dr. Milan Christopher, but come on, why would you choose some nerd over the star quarterback of Miskatonic University?)
Jenny Barnes - Rogues aren't exactly known for having great allies. Their only 0 XP ally who provides any kind of passive buff is Dario El-Amin, and the only other one with good utility costs 6 resources. So Jenny, being Jenny, doesn't necessarily mind Pete, however like the other Dunwich investigators she really needs to think carefully about her five off slots. Pete is great for her if combined with other agility passives like Track Shoes and The Moon • XVIII, and the horror healing for Jenny isn't nothing. However she'll often one way or another replace him with Lola Santiago down the line, so typically it's worthwhile to pick something else for those off slots anyway.
Preston Fairmont - Passive boosts are not Preston's style. While Preston has a tendency to fail tests, his deck-building is ridiculously tight and doesn't really have room for healing most of the time. You need to set up your economy engine, you need to get Well Connected or Dark Horse up ASAP. On top of that, because he starts the game with 9 resources in tow, Preston is the only investigator who can play Leo De Luca turn 1 without taking a 'gain a resource' action. There's just no room for you in Preston's club, sorry Pete.
Agnes Baker - Pete is a natural pick for Agnes. Usually Mystics need to rely on to do basically anything, but +1 allows Agnes to evade many monsters she can't kill with her main ability or Shrivelling, as well as protecting her from even more treacheries. On top of that, you need the horror sink in order to maximize the amount of horror put on Agnes in the presence of baddies (by minimizing the horror gained when alone). Don't take all the horror from that autofailed Rotting Remains if you can help it- give Pete a few remains, he'll totally forget about them next turn because that's just the kind of guy he is. Run two every time, and upgrade him before anything else because the +1 and +1 Sanity is literally the best upgrade Agnes could ask for.
Jim Culver - Like the other Dunwich investigators, Pete doesn't see much play in Jim decks because of how precious those five slots are. Jim also has additional methods of horror healing and his luck is often strictly better than anyone else's due to his passive ability, which combined with 4 makes horror not a large issue for him. He also can't take good advantage of the +1. His ally slot often goes to Olive McBride to take advantage of the modifier, or to Dr. Elli Horowitz since she can apparently play his Trumpet for him?? Elli is quite talented with all the Relics she just knows how to use.
Marie Lambeau - The +1 is actually not a bad fit for Marie decks, however the horror healing competes with much of what Marie wants to do. She needs allies who bring Doom in play, and unfortunately there's nothing Doomy about Pete's youthful physique. Arcane Initiate, David Renfield, and Alyssa Graham are all vying for a spot in a deck that will inevitably bury them when Baron Samedi shows up. This jazz club is just too crowded.
"Ashcan" Pete - Like other Dunwich investigators... oh wait a sec, Ashcan's a Survivor! And he doesn't compete for a slot with Duke! And his +1 rounds out Aschan's statline to all 4's with Duke in play (which is thematically fitting as well as mechanically satisfying). Heck, we could even call our deck The Adventures of Pete & Pete. Now, while Peter Sylvestre's horror soak tends to not be as big of a deal with Duke in play, there are still many Ashcan decks that like to run him. Most notably, the Desperate strategy which uses St. Hubert's Key and/or Meat Cleaver to get Ashcan's sanity down to 3 to play all the fun four icon cards. Sylvestre helps out a ton here by offering a permanent 1 soak per turn to keep Aschan AND Duke alive (because honestly once the doggo is gone there's not much hope left for Aschan). He's also often seen in Dark Horse decks alongside Madame Labranche, though I personally feel something like Track Shoes would be a better choice for a way to bring down your resource pool early while gaining +1. Outside of all of that, Aschan Pete is not the most natural choice for Sylvestre. Look for Survivors (or Finn) who really need the horror soak and boost first.
Calvin Wright - Calvin absolutely adores the horror soak Pete provides, as it helps sustain him when he's on the edge of death (which is exactly where you want him). This allows Calvin to use cards like Delay the Inevitable and Perseverance to protect his health, and Ward of Protection to deny health impacting treacheries you can't afford to test. The +1 is strange however, as it can work if you build Calvin towards evasion (which given the fairly lukewarm pool of weapons available to him is not a bad way to build him). A little physical trauma and maybe a Trench Coat, plus Pete in play, and before you know it Calvin can just evade before taking any actual damage. That said, Calvin decks are incredibly tight, and other allies like Madame Labranche (with Fire Axe) and later Yaotl will sometimes take priority, especially in Dark Horse decks.
Rita Young - This is one heck of a dynamic duo. Rita should be the absolute first choice for Peter Sylvestre among all the Survivors. +1, especially when stacked with Track Shoes (which Rita pretty much always runs) is beyond amazing. Rita can use that for her slew of ridiculously good evade based events: Belly of the Beast, Waylay, Slip Away, and Impromptu Barrier. You can turn that into fighting potential with Ornate Bow, which is miles better than any of her other weapon options. But that's not all. Peter's horror soak is amazing for Rita's 5 Sanity, and his upgrade helps get Rita's to a solid 4 to help protect her Sanity long term. Finally, Rita is another good candidate for a Desperate build alongside Meat Cleaver. She doesn't need Run For Your Life, but she'll happily run Say Your Prayers, Desperate Search, and Reckless Assault. Pete helps pretty much no matter how you choose to build Rita, and the fact that they both attend Miskatonic University makes it that much more thematically satisfying to run these two star athletes together.
Silas Marsh - Most of what I said about Rita applies to Silas as well- he's a great pick for Silas. While not built as well for evading, Silas is still a good choice for Desperate cards and Meat Cleaver, and not even a bad shell for Ornate Bow (though it conflicts with his high somewhat). Arguably he needs the horror soak more than she does with his 2, however he wont be evading as often. Given Silas' nature to include more skill cards and now Grisly Totem to help with skill checks, I'd say Silas doesn't need the +1 nearly as much. Still, an absolutely essential include if there's copies available of him for you to take. And yeah the upgrade should be high priority as well.
Wendy Adams - Even with Fire Axe and Dark Horse, Wendy has a lot of trouble fighting. Though Preston Fairmont also has 1, he can always trigger +6 on the Axe every turn if he wants to, while Wendy just can't. So most Wendy builds have to lean into evasion. Enter Peter Sylvetre. Stacking with cards like Track Shoes, The Moon • XVIII, and Trench Coat, Wendy can be made into an incredibly capable evader. While she doesn't need the soak nearly as much as Rita or Silas, she still appreciates it. Wendy is literally on the art for Waylay so you know exactly what to do.
William Yorick - Out of all the Survivors, Yorick enjoys Pete's company the absolute least. Sure, the +1 puts Yorck at a respectable 4, and sure he needs a way to deal with his low Sanity. However, Pete's competing both with other allies that enable Yorick's recursive ability as well as cheaper soak assets that can be more easily recurred. Yorick simply doesn't need Pete's comfort as long as Mr. Pawterson is in play, and when his Teddy Bear loses all of his fluff and at least one of his eyes falls off he can always dig up another one with the help of Beat Cop. Yorick is a strange creature.
There's also Lola Hayes, but I'm not well versed enough in playing Lola to even attempt to evaluate him there. My understanding is that only being able to trigger his ability on turns where she's a Survivor makes him a harder sell, and that Lola decks are usually combo based, so there's no room to run Pete.
So who are the best investigators to take Peter Sylvestre? Finn Edwards, Agnes Baker, Calvin Wright, Rita Young, and Silas Marsh. If you're playing any of these five, seriously consider running Peter in your deck, and if you're running any of them except Finn, definitely give him an upgrade.