Crimson Shade is a boss that appears in the Dimensional Vortex. it will fight alongside with Eggsterminator.
Crimson Shade is a Shade version of Lucca. Despite the fact that her techs have different names, the effects are the same.
Wearing a Red Vest and Red Plate against Fire elemental attacks in this battle is essential. Charming the Nova Armor from Crimson isn't worth it since the item is common in later levels and you having better equipment.
Your party will not only deal with Crimson, but also Eggsterminator. If you want to make the fight easier, quickly destroy the Eggsterminator first to minimize the status-immunity removal from equipment and status it inflicts.
If you received the Apocalypse Arm in this area and the Dragon's Tear from Lost Sanctum, you can quickly finish this battle with Robo doing 9999 damage, enough to almost 1-shot Eggsterminator and 2-shot Crimson.