The spell Rusted Blade reads:

You cause a rustlike patina to temporarily cover the target weapon. (Despite its name, the spell can affect any kind of weapon regardless of material.) For the duration of the spell, any living creature damaged by the weapon must succeed on a Fortitude save or contract filth fever (DMG 292). Use the spell's normal save DC for the initial saving throw, but use filth fever's normal DC 12 for later saves. Multiple applications of the disease do not stack, but even a creature that succeeds on one or more saves must continue to save each time it takes damage from the weapon. (Complete Mage, p. 116)

Filth Fever normally has an incubation period of 1d3 days before causing ability damage (1d3 Dex plus 1d3 Con).

Does the spell have this incubation period as well? In this case it would be absolutely useless for player characters: I mean, in case the PCs win, there is probably no opponent left to make a save. In case the opponents win, it is not really important if any of the victorious villains suffers from Filth Fever.

In that case the only use of this spell would be for NPCs who infect PCs.


1 Answer 1


That's correct—it doesn't

The question's assessment of the spell is accurate: that's how diseases work, and the 4th-level Sor/Wiz spell rusted blade [trans] (Complete Mage 116) makes no mention of changing how the filth fever it delivers changes due to the spell.

Compare the rusted blade spell with the 4th-level Sor/Wiz spell contagion [necro] (Player's Handbook 213) that causes the victim to suffer one increment of the picked disease's damage immediately—no incubation period—, and the spell rusted blade pales.

From a design standpoint that's not okay, of course, but there are thousands of spells, and some clever player can probably find a use for even a spell as lackluster as the spell rusted blade.

  • \$\begingroup\$ It would have to be a target that is freeble so that it does not make the Fortitude saves. It must not have access to cure disease. The use would have to be part of a plan some days in advance. An attack on the target has to be possible, but not outright killing it. So maybe you shoot a blowgun needle affected by "rusted blade" out of a dark alley at the old greedy noble who has never given to the gods and thus excluded from the clerics' services so that he catches filth fever and cannot attend the coronation of the new king and loses his power. Kingdom saved by "Rusted Blade"! What a spell! \$\endgroup\$
    – Giorin
    Mar 10, 2019 at 23:11
  • \$\begingroup\$ @Giorin The real problem with the spell is it's terrible duration—at 1 round/level, a madman can't even send his minions out on the streets with polluted blades to cause an outbreak or something. Even the skill trick mosquito's bite—which might be a way to infect someone with the disease then for the attacker to get away—still requires casting the spell by speaking in a firm voice and waving hands like kook, spoiling any surprise. I don't get it. Just pick a different spell, man. Pick a different spell. \$\endgroup\$ Mar 11, 2019 at 0:36

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