One of Reigns' objectives is to "Trick the Devil," and as you might expect, it's no small undertaking. Here's a step-by-step guide on how to befuddle Lucifer.
(This guide contains story spoilers for Reigns. Also, since much of your fate in the game is determined by RNG, getting the exact circumstances necessary to trick the Devil may take multiple playthroughs. Be patient and keep trying!)
-First, you need to get the "Doomed" achievement, which is acquired by "Unmask[ing] the Senator." When one of your nobles seems upset and asks you to follow him, do so.
-You're kidnapped, and then you flee your captors with the Senator's help. Follow the sound of the Senator's voice, but avoid running into the water.
-The Senator turns out to be a woman in white. When you return to the kingdom, you become lovers. Make sure your actions keep the church happy, since your relationship with the institution depletes each turn. In three years, the woman returns and tells you that you need to trick the Devil.
-At some point during one of your playthroughs, you may have met a witch who offers you a way to trick the Devil. If you ask her to share, she gives you numbers: 1043, 683, 1214, 842, 1432 and 1669. These correspond to years on the timeline. If you look at those years, you'll see alchemical symbols. The symbols represent the doors you find in the crypt: Fire, Arsenic, Acid, Gold, Pentagram, and Pentagram.
-Find and open the gold doors in the crypt (neutral doors usually lead to gold doors). Avoid arsenic doors unless otherwise instructed by this guide, as they often have traps. Find the torch; you may need to defeat the skeleton to do so. Use the torch, and you should see cracks in the walls when they appear.
-Go through the doors in this order: Fire, arsenic, then acid. Then go through the broken wall opposite of the gold door, then the door opposite of the pentagram, and then through the pentagram (Devil's) door.
-You'll meet Kloc, a friendly skeleton. Don't run away from him. Instead, "attack," which lets you talk to him. Kloc loves strawberries, which are unfortunately extinct, so it's time to grab some of those.
-At some point, your Doctor probably introduced you to his Vase. It needs to be "awakened," which you do by giving it a cold, red ruby. You get the ruby from the Witch as a reward for surviving 15 years of old age.
-Start a Crusade. The Vase will appear to you in Lamascus and, after a bit of conversation (it doesn't matter what you say during this time), it shows you a machine that brings things back to life. Ask for strawberries to be restored.
-Return to the crypt when you're able, and find Kloc the same way you did the first time. Give him the strawberries. From now on, he'll offer to help you whenever one of your resources gets low.
-You meet the Devil every 666 years, so plug on 'til the fated time. When he activates "Death Wish," keep saying "No" to everyone. When one of your resources is low, Kloc appears and offers assistance. Say yes!
-The Devil can't kill what's already dead, so he'll be thoroughly tricked, much to his chagrin. When the Devil reverts back to a plain old dog, say "Yes" to its barking. The curse is officially broken, and you receive the good ending and the achievement for stumping the Devil. Congratulations!
(Special thanks to App Unwrapper)