I am creating an encounter for a game I am DMing and am wondering how you calculate CR for a running battle. What I mean by this is that characters will be fleeing through a zombie infested town, with zombies popping up at regular intervals(every 2-3 rounds).

Theoretically, the battle would never stop, so it's effectively one encounter, but I don't think standard CR calculations would work. 15 CR 1 monsters at once is a lot harder than 15 CR 1 monsters in groups of 1-2 in a steady stream.

Any guidelines on how to calculate an appropriate CR in order to balance this?

  • \$\begingroup\$ Are you already familiar with the difference between Challenge Rating and Encounter Level? \$\endgroup\$ Apr 10, 2019 at 6:13
  • \$\begingroup\$ Apart from the EL vs CR issue already raised, your assumption re the difficulty of the encounter is not necessarily valid. Given area effect spells - even Burning Hands - and/or cleric/s to turn undead it can be easier for PCs to deal with weak enemies collectively rather than individually. \$\endgroup\$ Apr 10, 2019 at 12:36
  • \$\begingroup\$ Actual EL and CR, rather than the estimated one on paper, can also be affected by what type of characters are in the party, and their equipment, their condition. The more variables you have the harder it is to give a good answer. \$\endgroup\$
    – Aeyt
    Apr 11, 2019 at 3:40

1 Answer 1


It depends. If the encounters are started every 2-3 rounds and they don't overlap, I would not combine them with as if they were one encounter, as that's intended for concurrent enemies. You should take into account they cannot rest in between, but if they are otherwise separate encounters, the EL would be as if they were independent. If you anticipate them overlapping, but starting 2-3 rounds apart, then maybe determine EL at one encounter combined with the next. In any case, unless you anticipate all enemies surviving until the they are all present, definitely do not combine them all or it will be way too easy. Best of luck!

Unearthed Arcana began the idea of an XP budget, with Level-Independent XP awards, also used by PF and other RPGs, but I think this is a good application. Simply add up the XP and try not to hit them with more than 5 times a normal encounter, since that's all they should be able to handle before resting, but it's not a very accurate science since seemingly little things like special abilities or immunities can dramatically change things. Normal speed zombies might help mitigate this.

  • 1
    \$\begingroup\$ CR as the maximum of the number of enemies that are there sounds like a good idea. They should calculate the worst-case overlap for any given two encounters and use that as the CR for the total encounter. \$\endgroup\$
    – linksassin
    Apr 12, 2019 at 1:49

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .