Quote Originally Posted by Cleretic View Post
I don't think this is actually a clue, looking at the actual fights.

First of all, all three of those bosses use Grand Cross in their origin game, and crucially is basically the same in all three: laying down a truckload of status effects. They're actually three of only four bosses that use the ability (the fourth is the final boss of Tactics A2), and in each example is one of the defining attacks of the fight; it'd feel incomplete to not adapt Grand Cross in every case.

In XIV, all three bosses use Grand Cross completely differently; NED retains the status effect pile, but Ultima's Grand Cross drops the crystals that slowly explode into Bomberman-style plus signs, while Necron's is the stage-morph that creates rotating orbs that shoot lasers. The only connective tissue between the actual attacks is that Ultima and Necron's versions of it make cross shapes, but even then, they do it differently: Ultima's crystals emit the plus-shaped blasts, while Necron's orbs fire intersecting lines.

If we really want to ascribe worldbuilding meaning to every single version of this attack (which I should note is not something the game's ever done before this outside of Ultima the spell, which I think actually does do the same thing every time), I think the simple fact is that they're all named Grand Cross because they all have independent cause to be named Grand Cross.
Worldbuilding

They have treated fight mechanics in a diegetic way outside of Ultima. In Recollection, Sphene is literally giving raid callouts "keep moving," "the sigils channel magic" etc. In Pandaemonium, The Seventh Circle, Lahabrea is there to create a new platform for us to fight on before Agdistis breaks the one the party is currently fighting on. And then in Castrum Merinum, in the fight against Emerald Weapon, Gaius comments on the arena changing to Werlyt. So to me, it isn't too out of the question to consider that Nectron using Grand Cross means something, and that Calyx has some knowledge of the spell, or at least an interpretation of it, to be able to allow Necron to cast it. What it could mean, I don't know, but it is a little suspicious that there are some similarities between this version of Ultima, The High Seraph's Grand Cross, and this version of Necron's Grand Cross (summoning objects to create cross-shaped AOEs).