After the release of patch 1.20, Stoneskin II was removed and Stoneskin remained a Conjurer spell.
Stoneskin II was a Conjurer spell available at level 50. When used, the spell would bestow the Stoneskin status to all party members within an area of effect, however the spell could only be used outside of combat. The ability had a cast time 6 seconds and had a cooldown time of 2.5 seconds. Unlike Stoneskin, Stoneskin II was not a cross class ability and could only be used by Conjurers and Whites Mages.
Stoneskin II was originally added in response to player feedback about having to recast Stoneskin on each party member individually after falling in battles, a complaint that was also a joke among the development team when testing instanced encounters. It was added in patch 2.45.
After the release of the Stormblood expansion, Stoneskin and Stoneskin II were removed as abilities for players to use, primarily for balancing reasons among the three healers jobs. The ability has yet to make a reappearance in any form.
Stoneskin II is one of Y'shtola's unique Soul Breaks tied to the staff Thyrus (XIV) which at the expense of one Soul Gauge segment temporarily raises Defense and Resistance of all allies by 200%. If Y'shtola completes battles alive with Thyrus (XIV) equipped, she can eventually master Stoneskin II without needing to be equipped with the weapon in question to use it.