How often can one do a Knowledge check to identify a creature?

Question

The SRD section on Knowledge says:

Try Again

No. The check represents what you know, and thinking about a topic a second time doesn’t let you know something that you never learned in the first place.

How often can one do a Knowledge check to identify a creature?

• Once per encounter?

• Once each time a new creature shows up?

• Only the first time you encounter a creature?

• Can you retry when you gain a rank?

A couple of examples: Some undead show up. The Cleric fails his Knowledge (Religion) check.

• After a few rounds later some more undead of the same kind join the
  encounter. How is this handled?
• The cleric never increases his Knowledge (Religion), but a few days
  later, he meets the same monster. Can the cleric make another check?

Answer 1

Once, as a free action; either when the creature is first encountered or when the player declares they would like to make a check.

A character wouldn't get a retry on the check just because more of the same creature show up, whether during the same encounter or later that week. If the initial knowledge check determines that the cleric doesn't know what undead creature _______ is then seeing more of them won't help. Generally, a retry on knowledge checks is only allowed if the character gains another rank, or obtains some new information that could influence the check. For example, a ranger fails his check to identify a dryad; after tracking the dryad for a couple hours the ranger sees her tree-walk to a particularly large oak and place her hand on it fondly. In this case, the DM might allow a new check, which could represent the ranger recalling the connection between dryads and oak trees.

Answer 2

RAW: Once and for all.

Unfortunately, the Knowledge skill never got much love, despite how crucial information is to the game.

The rules are simple, simplistic really, and as you noted do not allow re-rolls. Ever.

This leads to 2 unfortunate effects:

• Each character should keep a complete list of all the Knowledge checks they did and their result, which is a lot of book-keeping.
• A character which does not know something at level 1 will still be ignorant of it at level 20, even if they spent all their free time trying to learn about it.

I would encourage any game to alter the Try Again entry. It's unlikely you'll come up with anything worse.

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My proposal: once per encounter, with additional rolls whenever additional information flows in.

Rather than treating a Knowledge check as what a character knows, I encourage treating a Knowledge check as what a character remembers right now. This helps with the verisimilitude, as it explains why a character could remember something once, but not later.

Mechanically, with regard to identifying a creature, I advise starting with the rules of the Knowledge Devotion feat (Complete Champion, p. 60):

Whenever you fight a creature, you can make a Knowledge check based on its type, as described on page 78 of the Player's Handbook, provided that you have at least one rank in the appropriate Knowledge skill.

You can make only one Knowledge check per creature type per combat. If you fight creatures of multiple types during the same combat, you can make one Knowledge check per type, thereby possibly gaining different bonuses against different opponents.

With a slight adaptation for forgetful characters:

1. Per-encounter tracking: to avoid lugging around an unwieldy list of everything each character knows or doesn't know.
2. Once for free, whenever a creature of this kind¹ first appears.
3. Once each time the creature exhibits a new ability².

I would also remind the Dungeon Master than they should feel free to give Circumstance bonuses at their convenience or to simply reveal information outright.

If the party already encountered a Formian Taskmaster an hour ago and it Dominated a party member, then upon recognizing another Formian Taskmaster the character should obviously remember that it may be able to Dominate a party member³.

Similarly, while a Knowledge (Religion) check covers all kinds of Undead, a character who has specifically spent time researching Mummies should be afforded a +5 or +10 Circumstance bonus⁴ on a check to identify Mummies.

¹ It's unclear whether the Knowledge Devotion feat really intends for a single check to be rolled for all Humanoids, regardless of whether they are Gnomes, Elves, Humans or Halflings or for all Outsiders (oO). I advise reading type not as the Type (Humanoid, Giant, ...) but instead as the Kind: for example, one roll each for a Formian Worker, a Formian Warrior and the Formian Taskmaster overseeing them.

² Unlikely to be game-breaking, and helps players feel better about their investment in Knowledge skills. For this purpose, ability means any Natural, Extraordinary, Supernatural or Spell-like Ability, which tend to define a creature, but not feats or skills which vary from individual to individual.

³ The DM should start by reminding the character of the abilities it already knows about the creature, either those it recalled or those it already witnessed. To avoid metagaming, the DM may ask the players what they know of the creature, and offer those abilities/facts first; even the best players may otherwise be tempted to act on information they know but their characters doesn't, such as fighting a Medusa blindfolded.

⁴ For each increment of +5 a check beats the DC, the character remembers one more ability or fact about the creature; thus it makes sense to use +5 bonus increments on the check for rewarding familiarity.

Answer 3

Once to represent what the character knew when the subject in question was first encountered in the campaign.

I don't think it's explicitly stated, but my interpretation of the RAW regarding the knowledge skill is that it represents the character's knowledge regarding anything that has been learned prior to their involvement in the scenario/campaign they are taking part in.

Once a character has encountered something and failed a knowledge check about it, the DM and player then have a solid baseline (i.e., this is a fresh topic/creature/concept to the character) on which to build further understanding through experience and research.