Extensive Alkahest was added to TERA's Valkyon Outfitters (cash shop) on the 14th of this month, to allow players to turn their EMP into a usable asset for game progression. There has been a lot of discussion regarding their true value, so I felt this would be a good time to give my knowledge out and hopefully help resolve confusion regarding the new system.
What is Its Purpose?
Based on the marketing around the Extensive Alkahest, its purpose is to be a universal ingredient for enchanting. What this means is that your item's tier, rarity and even its current enchant level are all irrelevant. Instead, you can carry a single type of alkahest and deal with all of your enchanting with it.
From an analytical point of view, a side-goal of these is to boost the game's economy and entice people to spend money on the cash shop. Since these are tradeable on the broker, this allows players to turn their cash into gold (although somewhat indirectly). A good way to look at it is just like Chronoscrolls, although one could argue that this is more beneficial in that it has actual in-game value (rather than just game time). I'll hit on that in a later article though.
Does It Enhance Enchanting Chances?
This is where things start to get tough. It's been stated that they boost the chances of success on enchanting (you can view one of the notices here). There's been some research done by different players, and while there's really no mathematics backing up the findings (as it is based on RNG), the concensus seems to be that the actual chance of succeeding an enchant is not increased, but the correction level is increased if you failed an enchant using the Extensive Alkahest. Again, there's really not enough information out from the real source (EME) confirming exactly how these work, and instead there is just the vague "Extensive Alkahest also give an increased chance to enchant your item" statement.
Extensive Alkahest or Masterwork/Refined?
This is really up to the player. Both Masterwork and Refined Alkahest are slimming down on the trader as of lately, and their prices are also below that of the Extensive. It's worth noting that you will still get correction bonuses on your fails regardless of whether you use "normal" or Extensive Alkahest, so the best way to judge which path to take is whether you want to purchase them (gold or cash), or just farm away in the game. Also consider that the Extensive might have better enchant chances, and they might even be changed later on as more players voice their concerns/praise for them.
Request From Readers
I would love it if some of you that do a lot of enchanting (sadly, that's not me!) could chime in on this with actual details. The one thing I've noticed that's been lacking is people posting the details of their enchant attempts, successes, etc. with similar items (ex iLvL 142 staffs) and different Alkahests.