There are some great campaign allies to get with Charlie. Usually they all have a and an extra incon.
In my opinion, one should consider the campaign allies when building a Charlie deck, so let's review what's available.
Spoilers incoming !
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NoZ : sadly Lita Chantler has no icons. Same for the Wayfarer allies from Edge of the Earth (only Anyu may be considered, but she has already a nice exhausting ability and won't get extra value from Charlie's ).
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Carcosa is the only campaign where you never get an ally. No, The Man in the Pallid Mask doesn't count.
 
Outside those campaigns, the other present you some nice options :
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In Dunwich, you have a lot of allies, notably Dr. Henry Armitage and his (he also generate ressources, which is great for Charlie who has to pay for all his allies), or Naomi O'Bannion (you like or ?) if you manage to earn her. Even with two Charisma you will not be able to take every available ally (Dr. Francis Morgan, Professor Warren Rice, Earl Sawyer and Zebulon Whateley) !
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Forgotten Age : even if you don't side with Alejandro Vela or Ichtaca, you can take Veda Whitsley, probably one of the best possible allies for Charlie : 1 cost, 3 health/horror, and a fantastic icons !!
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Circle Undone : a few possible allies but late in the cycle. Interesting part is you can focus on Penny, Valentino, Gavriella or Jerome depending of your role. Erynn MacAoidh is probably better for a real mystic.
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Dream Eaters : Randolph Carter (or Randolph Carter) is a solid ally. You will also encounter some allies without icons but they also don't take an ally slot (Virgil Gray and Richard Upton Pickman).
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In Insmouth you can have Elina Harper or Thomas Dawson depending of the scenarios. Elina's ability doesn't require to exhaust so it's full benefit.
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Scarlet Keys can give you Inspector Flint, Agent Ari Quinn and Dr. Dewi Irawan, but one could prefer keeping the exhausting for their abilities. Siding with the Coterie during the finale can also grant you a ton of slotless (and iconless) allies for free.
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Feast at Hemlock Vale's Residents are not Allies. You could get Helen Peters and Dr. Rosa Marquez, who bothe have nice icons and a flat bonus.
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The Drowned City gives you one ally after first scenario. Ruby Standish has a good exhaust ability if you don't need her bonus in mythos ; Andy Van Nortwick is great for clueing. John Raymond Legrasse is also a free bonus for the finale.
 
You can also play independant scenarios, consider playing those :
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The Blob that ate everything : Pet Oozeling doesn't take an ally slot. Pick it and forget Lt. Wilson Stewart.
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Machinations through time : Ezra Graves and Nikola Tesla are both great, especially if you are the cluer.
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The Midwinter Gala looks like perfectly tailored for Charlie. Full of 4-icons allies to talk with, and you can keep the best suited for your deck after (Agent Spécial Callahan, Archibald Hudson, Horacio Martinez, Arsène Renard, Miranda Keeper, Nova Malone, Claire Wilson, Delores Gadling, Thomas Olney, Dr Mya Badry, Elizabeth Conrad, Lucas Tetlow, Prudence Douglas, Raymond Loggins, Sarah Van Shaw).
 
Abbess Allegria Di Biase (Carneval of Horrors), John & Jessie Burke (Guardians of the Abyss) ,Lady Esprit (Rougarou), Sergeant Monroe (Excelsior) cost a bit too much imo. Keep your money and your slots for better allies (see the other review). André Patel (Film Fatale) has good icons but you probably prefer the exhaust him for it's ability.