diff --git a/code/modules/mob/living/simple_animal/friendly/mouse.dm b/code/modules/mob/living/simple_animal/friendly/mouse.dm
index 8348af43fa..340d2e5598 100644
--- a/code/modules/mob/living/simple_animal/friendly/mouse.dm
+++ b/code/modules/mob/living/simple_animal/friendly/mouse.dm
@@ -98,6 +98,16 @@
 		qdel(bigcheese)
 		evolve()
 		return
+	for(var/obj/item/trash/garbage in range(1, src))
+		if(prob(2))
+			qdel(garbage)
+			evolve_plague()
+			return
+	for(var/obj/effect/decal/cleanable/blood/gibs/leftovers in range(1, src))
+		if(prob(2))
+			qdel(leftovers)
+			evolve_plague()
+			return
 
 /**
   *Checks the mouse cap, if it's above the cap, doesn't spawn a mouse. If below, spawns a mouse and adds it to cheeserats.
@@ -123,6 +133,13 @@
 		mind.transfer_to(regalrat)
 	qdel(src)
 
+/mob/living/simple_animal/mouse/proc/evolve_plague()
+	var/mob/living/simple_animal/hostile/plaguerat = new /mob/living/simple_animal/hostile/plaguerat(loc)
+	visible_message("<span class='warning'>[src] devours the food! He rots into something worse!</span>")
+	if(mind)
+		mind.transfer_to(plaguerat)
+	qdel(src)
+
 /*
  * Mouse types
  */
@@ -169,3 +186,16 @@ GLOBAL_VAR(tom_existed)
 /obj/item/reagent_containers/food/snacks/deadmouse/on_grind()
 	reagents.clear_reagents()
 
+/mob/living/simple_animal/mouse/proc/miasma(datum/gas_mixture/environment, check_temp = FALSE)
+	if(isturf(src.loc) && isopenturf(src.loc))
+		var/turf/open/ST = src.loc
+		var/miasma_moles = ST.air.get_moles(GAS_MIASMA)
+		if(prob(5) && miasma_moles >= 5)
+			evolve_plague()
+		else if(miasma_moles >= 20)
+			evolve_plague()
+			return
+
+/mob/living/simple_animal/mouse/handle_environment(datum/gas_mixture/environment)
+	. = ..()
+	miasma()
diff --git a/code/modules/mob/living/simple_animal/hostile/plaguerat.dm b/code/modules/mob/living/simple_animal/hostile/plaguerat.dm
new file mode 100644
index 0000000000..16864ca9e6
--- /dev/null
+++ b/code/modules/mob/living/simple_animal/hostile/plaguerat.dm
@@ -0,0 +1,136 @@
+/mob/living/simple_animal/hostile/plaguerat
+	name = "plague rat"
+	desc = "A large decaying rat.  It spreads its filth and emits a putrid odor to create more of its kind."
+	icon_state = "plaguerat"
+	icon_living = "plaguerat"
+	icon_dead = "plaguerat_dead"
+	speak = list("Skree!","SKREEE!","Squeak?")
+	speak_emote = list("squeaks")
+	emote_hear = list("Hisses.")
+	emote_see = list("runs in a circle.", "stands on its hind legs.")
+	gender = NEUTER
+	speak_chance = 1
+	turns_per_move = 5
+	maxHealth = 15
+	health = 15
+	see_in_dark = 6
+	obj_damage = 10
+	butcher_results = list(/obj/item/reagent_containers/food/snacks/meat/slab = 1)
+	response_help_continuous = "glares at"
+	response_help_simple = "glare at"
+	response_disarm_continuous = "skoffs at"
+	response_disarm_simple = "skoff at"
+	response_harm_continuous = "slashes"
+	response_harm_simple = "slash"
+	melee_damage_lower = 5
+	melee_damage_upper = 7
+	attack_verb_continuous = "slashes"
+	attack_verb_simple = "slash"
+	attack_sound = 'sound/weapons/punch1.ogg'
+	faction = list("rat")
+	density = FALSE
+	pass_flags = PASSTABLE | PASSGRILLE | PASSMOB
+	mob_size = MOB_SIZE_TINY
+	mob_biotypes = MOB_ORGANIC|MOB_BEAST
+	var/datum/action/cooldown/scavenge
+	var/last_spawn_time = 0
+	///Number assigned to rats and mice, checked when determining infighting.
+
+/mob/living/simple_animal/hostile/plaguerat/Initialize()
+	. = ..()
+	SSmobs.cheeserats += src
+	AddComponent(/datum/component/swarming)
+	AddElement(/datum/element/ventcrawling, given_tier = VENTCRAWLER_ALWAYS)
+	scavenge = new /datum/action/cooldown/scavenge
+	scavenge.Grant(src)
+	var/list/mob/dead/observer/candidates = pollGhostCandidates("Do you want to play as the Royal Rat, cheesey be his crown?", ROLE_SENTIENCE, null, FALSE, 100, POLL_IGNORE_SENTIENCE_POTION)
+	if(LAZYLEN(candidates) && !mind)
+		var/mob/dead/observer/C = pick(candidates)
+		key = C.key
+		notify_ghosts("All rise for the rat king, ascendant to the throne in \the [get_area(src)].", source = src, action = NOTIFY_ORBIT, flashwindow = FALSE)
+
+/mob/living/simple_animal/hostile/plaguerat/Destroy()
+	SSmobs.cheeserats -= src
+	return ..()
+
+/mob/living/simple_animal/hostile/plaguerat/BiologicalLife(seconds, times_fired)
+	if(!(. = ..()))
+		return
+	if(isopenturf(loc))
+		var/turf/open/T = src.loc
+		if(T.air)
+			T.atmos_spawn_air("miasma=5;TEMP=293.15")
+	if(prob(40))
+		scavenge.Trigger()
+	if(prob(50))
+		var/turf/open/floor/F = get_turf(src)
+		if(istype(F) && !F.intact)
+			var/obj/structure/cable/C = locate() in F
+			if(C && C.avail())
+				visible_message("<span class='warning'>[src] chews through the [C]. It looks unharmed!</span>")
+				playsound(src, 'sound/effects/sparks2.ogg', 100, TRUE)
+				C.deconstruct()
+	for(var/obj/O in range(1,src))
+		if(istype(O, /obj/item/trash) || istype(O, /obj/effect/decal/cleanable/blood/gibs))
+			qdel(O)
+			be_fruitful()
+
+/mob/living/simple_animal/hostile/plaguerat/CanAttack(atom/the_target)
+	if(istype(the_target,/mob/living/simple_animal))
+		var/mob/living/A = the_target
+		if(istype(the_target, /mob/living/simple_animal/hostile/plaguerat) && A.stat == CONSCIOUS)
+			var/mob/living/simple_animal/hostile/plaguerat/R = the_target
+			if(R.faction_check_mob(src, TRUE))
+				return FALSE
+			else
+				return TRUE
+	return ..()
+
+/**
+  *Checks the mouse cap, if it's above the cap, doesn't spawn a mouse. If below, spawns a mouse and adds it to cheeserats.
+  */
+
+/mob/living/simple_animal/hostile/plaguerat/proc/be_fruitful()
+	var/cap = CONFIG_GET(number/ratcap)
+	if(LAZYLEN(SSmobs.cheeserats) >= cap)
+		visible_message("<span class='warning'>[src] gnaws into its food, [cap] rats are now on the station!</span>")
+		return
+	var/mob/living/newmouse = new /mob/living/simple_animal/hostile/plaguerat(loc)
+	SSmobs.cheeserats += newmouse
+	visible_message("<span class='notice'>[src] gnaws into its food, attracting another rat!</span>")
+
+/**
+  *Creates a chance to spawn more trash or gibs to repopulate.  Otherwise, spawns a corpse or dirt.
+  */
+
+/datum/action/cooldown/scavenge
+	name = "Scavenge"
+	desc = "Spread the plague, scavenge for trash and fresh meat to reproduce."
+	icon_icon = 'icons/mob/actions/actions_animal.dmi'
+	background_icon_state = "bg_clock"
+	button_icon_state = "coffer"
+	cooldown_time = 50
+
+/datum/action/cooldown/scavenge/Trigger()
+	. = ..()
+	if(!.)
+		return
+	var/turf/T = get_turf(owner)
+	var/loot = rand(1,100)
+	switch(loot)
+		if(1 to 3)
+			var/pickedtrash = pick(GLOB.ratking_trash)
+			to_chat(owner, "<span class='notice'>Excellent, you find more trash to spread your filth!</span>")
+			new /obj/effect/decal/cleanable/dirt(T)
+			new pickedtrash(T)
+		if(4 to 6)
+			to_chat(owner, "<span class='notice'>You find blood and gibs to feed your young!</span>")
+			new /obj/effect/decal/cleanable/blood/gibs(T)
+			new /obj/effect/decal/cleanable/blood/(T)
+		if(7 to 18)
+			to_chat(owner, "<span class='notice'>A corpse rises from the ground. Best to leave it alone.</span>")
+			new /obj/effect/mob_spawn/human/corpse/assistant(T)
+		if(19 to 100)
+			to_chat(owner, "<span class='notice'>Drat. Nothing.</span>")
+			new /obj/effect/decal/cleanable/dirt(T)
+	StartCooldown()
diff --git a/icons/mob/animal.dmi b/icons/mob/animal.dmi
index 68e6170969..34bd587146 100644
Binary files a/icons/mob/animal.dmi and b/icons/mob/animal.dmi differ
diff --git a/tgstation.dme b/tgstation.dme
index 298443fd4e..ebafd1e8e8 100644
--- a/tgstation.dme
+++ b/tgstation.dme
@@ -2810,6 +2810,7 @@
 #include "code\modules\mob\living\simple_animal\hostile\nanotrasen.dm"
 #include "code\modules\mob\living\simple_animal\hostile\netherworld.dm"
 #include "code\modules\mob\living\simple_animal\hostile\pirate.dm"
+#include "code\modules\mob\living\simple_animal\hostile\plaguerat.dm"
 #include "code\modules\mob\living\simple_animal\hostile\regalrat.dm"
 #include "code\modules\mob\living\simple_animal\hostile\russian.dm"
 #include "code\modules\mob\living\simple_animal\hostile\sharks.dm"
@@ -3621,6 +3622,7 @@
 #include "code\modules\vehicles\atv.dm"
 #include "code\modules\vehicles\bicycle.dm"
 #include "code\modules\vehicles\lavaboat.dm"
+#include "code\modules\vehicles\motorized_wheelchair.dm"
 #include "code\modules\vehicles\pimpin_ride.dm"
 #include "code\modules\vehicles\ridden.dm"
 #include "code\modules\vehicles\scooter.dm"
@@ -3632,7 +3634,6 @@
 #include "code\modules\vehicles\wheelchair.dm"
 #include "code\modules\vehicles\cars\car.dm"
 #include "code\modules\vehicles\cars\clowncar.dm"
-#include "code\modules\vehicles\motorized_wheelchair.dm"
 #include "code\modules\vending\_vending.dm"
 #include "code\modules\vending\assist.dm"
 #include "code\modules\vending\autodrobe.dm"