Earthblade is taught to you by an Npc on Megacorp Megaplanes after completing The Asian Treehuggers quest.
It is a stronger version of the Lightblade spell with metal damages replaced by earth damages and an added rooting effect.
Unlike it original version, it can be upgraded all the way up to Armagedon
Basic version
Damages : 1000 holy damages, 500 light damages, 300 earth damages
Cost : 1000 mana
Aoe : 4 meter in front of the caster
Effect : rooting (20 percent chances)
Armagedon version
Damages : 1000 holy damages, 1000 light damages, 1200 earth damages
Cost : 10k mana
Aoe : 8 meters in front of the caster
Effect : rooting (guaranteed)