Removes the horrible anim() proc and a bunch of spawns

code/modules/mob/mob_movement.dm

@@ -236,14 +236,12 @@
 				L.loc = locate(locx,locy,mobloc.z)
 				var/limit = 2//For only two trailing shadows.
 				for(var/turf/T in getline(mobloc, L.loc))
-					spawn(0)
-						anim(T,L,'icons/mob/mob.dmi',,"shadow",,L.dir)
+					PoolOrNew(/obj/effect/overlay/temp/ninja/shadow, list(T, L.dir))
 					limit--
 					if(limit<=0)
 						break
 			else
-				spawn(0)
-					anim(mobloc,mob,'icons/mob/mob.dmi',,"shadow",,L.dir)
+				PoolOrNew(/obj/effect/overlay/temp/ninja/shadow, list(mobloc, L.dir))
 				L.loc = get_step(L, direct)
 			L.setDir(direct)
 		if(3) //Incorporeal move, but blocked by holy-watered tiles and salt piles.