Path of Exile 2 Cruel Difficulty - Secret Bosses and Permanent Upgrades Guide (Acts 1-3)

A Work in Progress
Quick note: PoE2's early access means the game's evolving fast. The campaign you play through today might have new secrets tomorrow. I'm keeping this guide fresh with every major update, so bookmark it if you want to stay in the loop.
Cruel Difficulty: Hidden Treasures of Act 1 Act 1 packs some serious upgrades: 4 passive points, cold resistance, and a significant life increase. Here's your treasure map:
Beira and her Rotten Pack still lurk in Clearfell, now guarding 10% cold resistance. In the Hunting Grounds, Crowbell's waiting to give up 2 passive points. Una's still lost her lute in Ogham Farmlands - return it for another 2 points. Finally, wake Candlemass in Oghman Manor with the Psalm of Madness, and defeat him for a whopping 8% life increase.
Act 2's Greater Challenges More power awaits: 4 passive points, lightning resistance, and a choice that'll shape your build.
The Kabala quest chain starts in Keth - slay their queen for 2 passive points. You'll need both Kabala and Sun Clan relics from the Valley of Titans region. Bringing both to the altar lets you choose between:
Deliver the Final Letter in Deshar for 2 more passive points, and seek out the Sisters' Shrine in the Spires for 10% lightning resistance.
Act 3's Ultimate Rewards The stakes are higher: 4 passive points, fire resistance, 40 spirit, and another build-defining choice.
Mighty Silverfist guards 2 passive points in the Jungle Ruins. The Azak Bog's witch, Ignagduk, holds 40 spirit and drops a guaranteed Uncut Spirit Gem on first kill.
In the Venom Crypts, Servi offers three powerful options after receiving the Venom Vial (choose wisely - it's permanent!):
For fire resistance, take down Blackjaw in Jiquani's Machinarium (you'll need a Small Soul Core first). Last but not least, sacrifice a Heart from Aggorat or Utzaal for your final 2 passive points.