diff --git a/code/modules/mob/living/basic/mining/hivelord.dm b/code/modules/mob/living/basic/mining/hivelord.dm
index c15016ebab6..91048b985d9 100644
--- a/code/modules/mob/living/basic/mining/hivelord.dm
+++ b/code/modules/mob/living/basic/mining/hivelord.dm
@@ -261,7 +261,7 @@
 /mob/living/basic/mining/hivelord/legion/advanced/tendril
 	from_tendril = TRUE
 
-// Legion that spawns Legions
+// Big legion (billy)
 /mob/living/basic/mining/big_legion
 	name = "big legion"
 	desc = "This monstrosity has clearly been corrupting for centuries, and is looking for a fight. Rumours claim it is capable of throwing the strongest of miners and his name is Billy."
@@ -280,6 +280,7 @@
 	attack_sound = 'sound/misc/demon_attack1.ogg'
 	speed = 0
 	butcher_results = list(/obj/item/regen_mesh)
+	ai_controller = /datum/ai_controller/basic_controller/big_legion
 
 /mob/living/basic/mining/big_legion/melee_attack(atom/target, list/modifiers, ignore_cooldown)
 	if(!isliving(target))
diff --git a/code/modules/mob/living/basic/mining/hivelord_ai.dm b/code/modules/mob/living/basic/mining/hivelord_ai.dm
index 735442e2259..083f16873e9 100644
--- a/code/modules/mob/living/basic/mining/hivelord_ai.dm
+++ b/code/modules/mob/living/basic/mining/hivelord_ai.dm
@@ -61,6 +61,23 @@
 		/datum/ai_planning_subtree/basic_melee_attack_subtree,
 	)
 
+/// Big Legion
+/datum/ai_controller/basic_controller/big_legion
+	blackboard = list(
+		BB_TARGETING_STRATEGY = /datum/targeting_strategy/basic,
+		BB_TARGET_MINIMUM_STAT = DEAD,
+		BB_AGGRO_RANGE = 5,
+	)
+	ai_movement = /datum/ai_movement/basic_avoidance
+	idle_behavior = /datum/idle_behavior/idle_random_walk
+	planning_subtrees = list(
+		/datum/ai_planning_subtree/random_speech/legion,
+		/datum/ai_planning_subtree/simple_find_target,
+		/datum/ai_planning_subtree/attack_obstacle_in_path,
+		/datum/ai_planning_subtree/basic_melee_attack_subtree,
+		/datum/ai_planning_subtree/find_and_hunt_target/prowl/lavaland,
+	)
+
 /// Don't run away from friendlies
 /datum/ai_planning_subtree/flee_target/legion