First off, what are codexes? Codexes are items that you can purchase using Tokens of Favor that stick with your account permanently. Once you buy one, you can use it for all subsequent characters. You can buy and equip them at the beginning of every run and at the end of each level, and only one can be equipped at a time.

Below is a list of every codex with its in-game description, as well as a small description of what effect it gives. This list is as-of-yet unfinished, but it will be updated as new information is discovered.

The term "exhaustion" will be used in this guide describing when an action depletes your maximum stamina, or rather when a codex reduces the amount of exhaustion caused by an action, meaning that it reduces the amount of stamina that is depleted by the action.
Exhaustion will only be used when maximum stamina is involved. The word stamina will be used where the codex only affects normal stamina degradation.

This information originally stems from a reddit thread I created here, and much of it was found by Mr. Stealthy (formerly /u/dataminerandtester on reddit). Discussion relating to the effects of any of the codexes is encouraged, especially relating to the ones that are currently unknown. There's only so much one group of people can get done, so any help from the community is appreciated.

And if you're looking for more info on Necropolis, check out the wiki[necropolis.gamepedia.com]. It has information about items, weapons, armor, lore, enemies, and more. Go ahead, take a look and learn something new.

Man, I ain't hungry. I already ate three weeks ago.

Stamina cost of attacking is halved.

Getting someone to see red is dangerous. They keep swinging until they can't. Thing is when they do that, it's easier to hit back.

Lowers Armor value by 1, decreasing max HP and increasing damage taken; increases damage output and aggro potential.

You don't want to part with it, and I don't want to pay for it. Let's meet in the middle.

Lowers vendor prices by 30%.

Drink your way to a "healthier" you. Blood is the answer you're looking for!

Regenerate health upon hitting an enemy. The amount of health gained = 5% of damage inflicted.

Don't feel the burn. Instead, take it easy for a second and get back to fighting sooner.

Double stamina regeneration rate.

Throwing up is amateur hour. Eat it, and make it stay down. Show the food who's in charge.

Prevents vomiting when consuming rotten food. (Testing has shown that this may not actually be the case, so this isn't confirmed and I don't actually know for sure what it does.)

Jumping is easy, just push off the ground. Dodging is just a little scamper in one direction. It'll take way less effort if you follow my easy five step agility training plan.

Halves the stamina cost for dodging, sprinting, and jumping.

Once you know the secret to power attacks, you'll be able to bust them out all day without feeling a thing. Show-off.

Reduces exhaustion from power attacks.

KAMAF FACE ENEMY HEAD ON. KAMAF STAY STANDING TALL AGAINST ANY* BLOW. *NOT GUARANTEED

Makes it harder for you to be staggered/knocked down by enemy attacks.

There's this place. Different on every monster, but if you can hit that place, they totally fall over. Pretty useful.

Not yet confirmed. Grants the "Sharpshooter" trait, and the value for SharpshooterTraitValue is 2, so I'm going to assume the simplest answer and say that it doubles damage done by ranged weapons. If anyone has evidence for or against, let me know.

If you hold it up in the right spot, you can absorb an amazing amount of force. With this technique, you can stop letting those blows tire you out so much.

Stamina cost for blocking is halved.

Make sure your feet are shoulder width apart, planted on the ground. And slightly bend the knees. There, now you won't get knocked down.

Makes you immune to being knocked down, but you can still be staggered.

KAMAF HIT GOOD. THING GO DOWN. YOU HIT GOOD. THING GO DOWN. GOOD.

Increases your ability to stagger/knock down enemies.

Ever notice that sometimes your stamina just feels tapped out? Mr. Monk can help. Just remember, there are no quick and easy solutions when it comes to complete inaction.

Passively regerates max stamina.

You're wondering what the scribbles on that foldy brown thing mean? Or what the potion with the gross chunks in it does? Here's the scoop.

Automatically identifies would-be unknown items.

I can totally make that jump. Totally. Now you can too!

Greatly increases jump height.

That red stuff is important, and it will keep you going. If you focus on it, you can slowly recover from any wound. (Except the fatal ones.)

Slow passive health regeneration. (1% every 10 seconds)

In section one, we look at the fall. Where are you falling (an abyss, a fiery chasm, into some beast)? In this, you find the key.

Fall damage taken is halved.

(Unconfirmed) Areas below you are visible from farther away. (Suggested by HunterVincentDark)

The feel of a gem in the pocket is second only to the feel of two gems in the pocket.

Doubles the value of all gems picked up.

You beat it, you eat it. A survivor's guide to cooking and crafting in the Necropolis.

Unlocks crafting recipes for all potions. Recipes for items other than potions, such as food and projectiles, are not unlocked by this codex.

If you have any questions or comments about the guide, be it asking for clarification or fixing a grammatical error or whatever else, feel free to post a comment and we'll try to adress it as soon as possible.