Pleroma Grass (プレロマ草) is a legendary plant growing directly on top of septium veins.
Pleroma Grass is the main ingredient for Gnosis, the nostrum used by the D∴G Cult to realise their ambitions. The grasses grow in abundance on the southern marshlands of Crossbell.
Because the azure colour of normal Pleroma Grass matches the colour of Blue Gnosis, it can be assumed that the vermillion variant is used in the creation of Red Gnosis.
Red Pleroma does not appear until the Finale of Ao no Kiseki's New Game+, where the cryptid Vermillion appears in the Vermillion Wetlands after defeating the other five hidden monsters.
In Trails of Cold Steel III, Red Pleroma also appears in the catacombs below Heimdallr as well as other areas throughout Erebonia, though the circumstances behind that are still unknown. During the finale, as the Curse spreads throughout Erebonia, a new Black Blaze Pleroma is introduced as appearing all over Erebonia.