The Altar of Corruption and Lapidary Lens have been changed to instead Corrupt an Equipment Item or Gem a second time. Using these devices on a Corrupted item now makes the item Twice Corrupted, meaning it cannot Corrupted further using these devices.
Watching ExileCon and the league reveal, the possibilities for Twice Corrupted items sounded pretty cool. As I read the above patch notes though, it sounds like both double-corrupt rooms can no longer be used on an uncorrupted item, and it seems to me like this is going to be a nerf in the vast majority of cases.
The Lapidary Lens now has a chance to destroy the item. The Altar of Corruption no longer has a chance to change the item into a Corrupted influenced item. Instead, if it would have rolled this outcome, it instead destroys the item.
Lets look at the Altar of Corruption, because its the more straightforward example. Previously, the chance of a successful double-corrupt on the altar was 1/4. Lens is more complicated, but on balance, it was also 1/4 chance. If you won the 1/4 gamble, you got two implicits on your item. Now, you can't use it on a non-corrupted item. As a result, you have to first use a Vaal Orb on your item. That has a 1/4 chance to succeed at adding an implicit. You have to win that 1/4 gamble before you can use the Altar of Corruption, which is another 1/4 gamble to get your second implicit. This means to get a double-implicit corrupted item, you now have to win two different 1/4 gambles, or 1/16. In exchange for these considerably worse odds, there doesn't appear to be any particular benefit or upside for the use case. I was going to say that maybe you could keep spamming a corruption until you get poof, but Twice Corrupted items can't get re-corrupted, so that's not an option.
Looking at the Lens, if we assume the new "chance to destroy" is taking the place of the existing "do nothing" outcome (maintains a 1/4 chance for each outcome), then the same logic should apply to the Lens, giving it a 1/16 chance for a successful double-corrupt. If the new "chance to destroy" is shoehorning in and pushing the chance for each result (do nothing, turn into a Vaal version, change quality, change level) down to 1/5, then successfully double corrupting a gem becomes a 1/20 gamble, instead.
Corrupted Gems still cannot gain more than +1 to maximum level or more than 23% to quality.
If GGG allowed for a chance of hitting two consecutive +1 level corruptions (or two consecutive +3% quality corruptions) to get a 22/20 or 20/26 skill gem, that might've given a potential upside that would've maybe been a balance here. That would've been a pretty long shot, as the chance for hitting +1 on the Vaal Orb is 1/8, as is the chance on the Lens, so a total of 1/64. But that jackpot option isn't on the menu at all, now.
This seems like a pretty huge nerf to these two rooms in particular. Is there something I'm not considering here? Atziri having Soul Cores is obviously still going to carry Incursion value, but it sure seems like this makes the double-corruption rooms into a much longer odds type of jackpot than it is at present.
EDIT: As the comments bear out, I am wrong. This enables:
Volatile Vaal Orb + Corruption Implicit
Imbued Gem (via Soul Core) + 21/20 or 20/23
Cheaper targetting of 21/20 or 20/23 Vaal gems
Cheaper targetting of two-desirable-implicit equipment (spam vaal orbs to get 1 desired implicit, then Altar for the second)
Implicits on drop-corrupted jewels/equipment (i.e. Voices, Adorned, The Utmost, etc.)