[RPG] How much should this Infectious Zombie homebrew change a zombie’s challenge rating


When you are bitten by a zombie, you have to make two checks against Fort DC 10+HD of the zombie. If one fails, you turn into a zombie in 1d4 days, if both fail, you turn into a zombie in 1d2 days. In 1d4 hours your base land speed drops by 33%. In 2d8 hours after that, you take a -3 penalty on reflex saves.

This homebrew is meant for an ECL 1 DnD 3.5 zombie survival campaign. I want to know how much I should (or even if I should) change zombie CR by.

EDIT: I will use the zombie plague but with the following modifications:
The infected automatically die in 3d4 days if they don't stave off the disease.
The DC is 10+HD

Best Answer

This should be an enormous increase in CR.

Basically, you're giving every attack the zombie makes a "save twice or die" effect. Unless there's some easy way to cure this infection outside of combat, your entire party will be dead within a week.

There's a reason Left 4 Dead and some other zombie games/media often imply or outright state that the main characters are, for whatever reason, immune to (or asymptomatic carriers of) the zombie disease: not being immune makes survival mostly a matter of being very, very lucky.

Let's say a character gets attacked by 4 zombies. Each zombie has only a 25% chance of hitting the character, and the character has only a 25% chance of failing their save. Further, let's say that each time all the surviving zombies have attacked, the character kills one (so the character is attacked 10 times: 4+3+2+1). If they only have to save once to be safe, the character only has a 52% chance of not being infected at the end of the fight; if they have to save twice, it's a 31% chance. And that's a single fight.

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