(Gameplay) Nasus's Spirit Fire vs. Jungle Monsters

When a jungle monster is affected by Doge's spirit fire, they sometimes lose twice, or thrice the armor they are supposed to, at first, they lost the normal amount of armor but after repeated clears they lost twice, then thrice as much armor as spirit fire reduces. I didn't test this very much, but in all the games it occurred I bought stalker's blade (did not try to get it to happen without it).