Bastion's Undead Artillery

You create 4 large orbs of Necrotic energy. Causing them to come crashing down at points you designate within range. Each creature within a 40 foot radius sphere centered at each point must make a Constitution saving throw. Taking 10d10 Necrotic damage on a failed save. Humanoids killed by this damage immediately rise up as an undead. If it has 2 or fewer hit dice remaining it becomes a zombie, if it had 3-5 hit dice it becomes a ghoul. Otherwise it becomes a wight. All undead created in this way are friendly to you and obey your commands for 1 hour. After which they collapse and die