It is RECIPE, which you can obtain for tokens in Infinite Archive.
You need Infinite Archive Challenger achievment to get ability to buy it.

There will be introduced new Grand Master Crafting Station, you need Grand Master Crafter achievment to get ability to buy it for vouchers from Rolis Hlaalu

Grand Master Crafting Station will be brand new crafting station, where you can craft UNIQUE items with UNIQUE mechanics, and Rebirth Soul Gems will be 1st step in this direction

Rebirth Soul Gems will be items which bring some IA mechanics in overland/trials/dungeons

Mechanics: You can craft Rebirth Soul Gems, which is CONSUMABLE item, after using that you get buff for 1 hour, which gives you possibility to REVIVE one time after being killed with special revive mechanics. Every class have its own revive effect. After you have been ressurected, you get debuff for 24 hours which does not allow you to use Rebirth Soul Gem

Instead of death you stay in place for 5 (10) sec with immune to damage and crowd control and (for example)

-DragonKnight - you go to dragon leap form with wings which cover you, with active fire aura which burn enemies in 10m radius (burning status effect) (like Iron Atronach form in IA)
-Nightblade - remember Elden Hollow dark portal which looks like black hole? NB, as The Lord of Shadows became this Essence of Shadows, pulling monsters, damage them by Bleeding damage, like Exsanguinate verse
-Arcanist - became the Knower's Eye, taunt all nearby enemies and damage them by lasers which fires in monsters and deal Oblivion damage
-Sorcerer - became pure Lightning. Just copying Tempest verse and damage all nerby mosters with lightnings.
-Warden - became Ice Avatar statue, freezing everything in battlefield
-Templar - became pure light, copying light Fabled aura, burn every enemy in it and give immune to damage to allies standing in it
-Nercomancer - became undead lich and summons hordes of skeletons (or crystals which blow in few seconds)

Crafting: it will be expensive. There will not be 100% chance of succesful craft.

-DK: Class stones - Fire Opal + Garnet
-NB: Class stones - Bloodstone + Ruby
-Arc: Class stones - Chysolite + Emerald
-Sorc: Class stones - Sapphire + Amethyst
-Warden: Class stones - Turquoise + Jade
-Templar: Class stones - Citrine + Almandine
-Necro: Class stones - Sardonyx + Quartz

Diamond+Carnelian reserved for new class

You need 200 Fire Opals + 200 Garnet + 200 filled soul gems for 50% chance to craft DK Rebirth Soul Gem (for exmaple)
(40/40/40 minimum for 10% chance)

Few points why i want this
-MORE CLASS IDENTITY
-usage of useless items
-it will shake trading in game
-i do not like one shot mechanics, not everything you can control in mmo - latency, server lags, provider lags and so on. i have limited time to play and i want option that could help me to complete activity
-introducing new Grand Master Crafting Station with unique items with unique mechanics that will shake gameplay
-Feeling of progression
-....why not? i think its fun!

Also, there should be an option in group finder that disable this mechanic for those who want pure trifectas (or trifecta achievment wont count for players who use this item in dungeon/trial)

So many things that i also want to write here about this idea,but main idea - i hope i explain it and you understand what i mean

Lets discuss )

Sorry for my english.