Vexcalibur is a Lightfall-exclusive exotic glaive obtained after completing a mission called The Variable! You must have already completed any version of the Lightfall campaign in order to have access to this quest. There will be a total of 3 exotic catalysts to obtain for this exotic.
More information will be provided here as it becomes available!
You must be 1750+ Light Level for normal and 1815+ for Legendary
You must own the Lightfall DLC and have already completed the campaign