Spell found - from a Dark Elf magic user...

So, the players in my current AD&D game found some interesting treasure (some of it ties into a sort of plot I have been working on for the campaign, as long as it lasts).  One of the items was a unique spell that was written by a Dark Elf magic user.

The spell is a 2nd level MU spell called Plague Rats.  It is for creating a special type of Giant Rat that will be especially effective at destroying or reducing to ruin a small habitation.  If employed by a much higher level magic user, it could be used to destroy a larger habitation, or even large amounts of countryside.  The problem becomes (1) working with giant rats, and (2) avoiding any competent defenders (like NPCs or Characters).

Here is the spell -

Plague Rats (alteration)

Level: 2	Components: V, S, M
Range: 20'	Casting Time: 2 rounds
Duration: Special	Saving Throw: None
Area of Effect: 2d6 Giant Rats

Explanation/Description: This spell is cast on a number of Giant Rats within 20' of the caster.  Upon completion of the spell, the Rats are then infected with a curious plague effect.  If they score a hit in combat on someone, in addition to normal damage, the victim must make a saving throw vs. poison, or become infected by the special effect of this spell.  If the victim fails their poison saving throw, then for four combat rounds following the one during which they were bit, that person will become unnaturally sympathetic to giant rats.  They will not be inclined to attack them, to consider them a threat or menace, or even to want to distance them self from such creatures.  During this time, if they are actually attacked by a giant rat, they can resist the sympathy, and if they successfully roll 1d20 beneath their intelligence, they can attack the giant rat that bit them, during that round.  They must roll each round.  Each time another rat bits the victim, if they fail their saving throw, the effect of this "sympathy poison" is extended another four rounds.  Rats under the influence of this spell have curious luminescent red eyes.  The duration of the spell is based on the level of the caster: Level 3-4 it lasts 3 turns (30 minutes); levels 5-6 it lasts 3 hours; levels 7-8 it lasts 3 days; levels 9+ it is permanent. Material components are a piece of fabric (kerchief, piece of tunic, wound dressing) that was owned/used by a person who died from a disease.  It is consumed during the casting of the spell.