I'm intending on making a hydrus/lycanthrope creature, and I'd like to know about how the hydrus's poison DC advances.

I notice that poison DC tends to be (10 + ½ Hit Die + Con modifier), but is there actually a rule in common for that? If so, where's it located? Otherwise, how should the poison DC increase into the late game?

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    \$\begingroup\$ These look like two separate questions about two totally different mechanics. You will probably have better luck editing it to ask one question, and open a second question for the other. \$\endgroup\$
    – Tritium21
    Commented Dec 9, 2015 at 5:06
  • \$\begingroup\$ Welcome to the site. An interesting question. One of the struggles in answering this may be the abbreviated nature of the creature entry. The third-party product in which the hydrus originally appears is John Brazer Enterprises's Book of Beasts: Monsters of the River Nations, and any respondent will likely need that rather obscure book to answer your question exactly. The feat Improved Invasion, a hydrus bonus feat, isn't on the d20PFSRD. \$\endgroup\$ Commented Dec 9, 2015 at 12:41
  • \$\begingroup\$ Man, now I can't stop thinking about making my Halfling Cleric a were-Hydrus and eating people from the inside. \$\endgroup\$
    – GreySage
    Commented Dec 9, 2015 at 22:51
  • \$\begingroup\$ I've edited this to narrow it down to just one of the questions, specifically the one about poison. Does it look sensible, and Gavin, does it capture what you want to ask? I suggest you ask about the hydrus infestation thing in a new question. \$\endgroup\$ Commented Dec 17, 2015 at 8:21
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    \$\begingroup\$ @doppelgreener I really do want to see that were-hydrus halfling question posted separately. \$\endgroup\$ Commented Dec 17, 2015 at 14:45

1 Answer 1


The Universal Monster Rules on poisons says

A creature with this ability can poison those it attacks. The effects of the poison, including its save, frequency, and cure, are included in the creature’s description. The saving throw to resist a poison is usually a Fort save (DC 10 + 1/2 the poisoning creature’s racial HD + the creature’s Con modifier; the exact DC is given in the creature’s descriptive text). Poisons can be removed through neutralize poison and similar effects.

Emphasis mine. That's pretty much where the standard poison DCs are introduced.

Note that in Dungeons and Dragons 3.5, the spell poison followed a similar pattern in determining its DC but substitutes Wisdom for Constitution; the Pathfinder spell poison instead uses the standard spell mechanics to determine the spell's saving throw DC but also uses Pathfinder's more complicated rules for poisons as afflictions.


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