Crafting Level 21 Skill Gems

Introduction

Welcome Aspirants!

Let's learn how to make something this beautiful:

This is meant to be a quick and clean guide for self-crafting Level 21 skill gems. Early in a POE2 season, this can be an expensive process due to the cost of Perfect Jeweler's Orbs early. Later on, this is a cheap method to up your DPS and effectiveness in every slot. At the bottom, I have FAQ and links to get assistance with this craft, any craft, and your builds. GL GL

Materials and Cost

The cost of scoring a successful level 21 gem will vary significantly over the course of the season. And, success itself is a pre-defined gamble. Here is a quick breakdown of what you'll need and the approximate value.

For cost estimation I will not itemize the price of each currency, but will say that you need 6 gems on average to slam with an Omen of Corruption to "expect" a +1 result. Again, this is chance, so you could hit it on your first try, and you could hit it on your fifteenth try.

For materials you will need the following for each attempt:

1 Uncut Skill Gem (lower level, see Step 1 below)

4 Gemcutter's Prism

1 Jeweler's Orb (Plain, Greater, or Perfect, depending on your need)

1 Omen of Corruption (optional, but see Math section in Appendix)

1 Vaal Orb

Chance for +1 Outcome, Probabilities

The chance for the +1 outcome with an Omen of Corruption is ~16.67%. I'm going to breakdown the math for the outcome in an appendix section of this guide. I'll also include comparisons of using the Omen of Corruption and not using it, in case you are debating. See bottom for details.

Step 1: Cut Lower Level Gems

The amazing part about this craft is that you don't need to start with a Level 20 Uncut Skill Gem. You can start with any level, and then UPGRADE it AFTER you get the result you want. I tend to have a massive pile of Level 17 and 18 Uncut gems, so I use those to cut copies of the gem I want to craft.

You will have to click the "All Gems" tab on the Gem Cutter menu if you already have that Gem equipped in order for it to show up.

You'll also likely need to accept this confirmation message:

NOTE: you do need to Quality and Jeweler these gems prior to the Vaal step, so here you can make a choice of cost-efficiency vs time. If you want the most cost-effective process, do these 1 gem at a time. If you want a time-effective method, do these in batches of 4-6 at a time.

Step 2: Quality and Jeweler's

Next you will likely want to max out the quality of the gem to 20% and upgrade the socket links of the gem, most likely to a Perfect Jeweler's.

Step 3: Omen and Vaal

Now highlight your Omen of Corruption and use the Vaal Orb.

Step 4: Upgrade Successful Gems

For any gem where you succeeded in getting the +1 Gem Level outcome, you'll now want to upgrade those with a Level 20 Uncut Skill gem, which will bring it from the lower level you started with up to the maximum Level 21.

Step 5: Reminder About Probabilities

That's the end of the craft if you succeeded, but remember that you can get very or unlucky, and if you fail, just keep on plugging away. GL GL

ASSISTANCE

If you want further help with this crafting, or have any suggestions / thoughts / comments, I actively manage a well-curated Discord server with a dedicated crafting channel, come find us and feel free to @ me directly with questions:

http://discord.gg/nNPcpZqcBj

I stream weekly and will answer any questions live. Am on Twitch and YT:

https://www.youtube.com/@ignatiushs
https://www.twitch.tv/ignatiushs

Breaking Down the Math

The chance of achieving a +1 gem level outcome when corrupting a skill gem using a Vaal WITH an Omen of Corruption is 1/6, or approximately 16.67%.

This is calculated based on the corruption mechanics for skill gems: there are typically four main outcome categories (no change; level change, which is equally likely to be +1 or -1; socket change, which is equally likely to be +1 or -1; and quality change, which is equally likely to be positive or negative). Without the omen, each category has a 25% chance.

The Omen of Corruption removes the "no change" category, so the remaining three categories each have a ~33.33% chance. Within the level change category, there's a 50% chance of +1 level specifically, yielding 33.33% × 50% = ~16.67% (or exactly 1/6).

To expect at least one +1 outcome, you'd need to corrupt roughly 6 gems on average. This is because, for a success probability p = 1/6, the expected number of independent trials until the first success in a geometric distribution is 1/p = 6. Again, these are PROBABILITIES, not guarantees. You are spinning the wheel here and those of you who get extremely unlucky will come to Discord to let us know. XD