Keen weapon?

[Hurnn]

Is it a worth while enchant?

[Urpriest]

Luckily, it's just a bonus to damage when your attack roll passes a certain threshold. So it's just a matter of calculating how much damage it adds, compared to other special abilities. It can be good for certain characters, but it isn't always. Be aware that there are spells that grant it, which may be a better solution than spending a +1 on it.

[Sayt]

There's also a feat which does it.

Generally speaking, you'd get Keen on weapons with high native ranges like scimitars or elven curve blades. Alternatively, it might also be good on weapons with high multiplers like scythes or Warhammers.

My favourite, though, is deepwood sniper 2, which makes, for instance, a dwarven great crossbow a 15-20/x4 monstrocity (assuming you have access to material which slightly validates crossbows, like pathfinder's crossbow mastery, crossbow sniper, splitting and such.

[Djinn_in_Tonic]

Keen is worth a +1 bonus which, at most, can get us a reliable 3.5 damage (Flaming or similar enchantments).

Note that keen becomes less useful as our chance of confirming the critical hit decreases. Its value is (keen Critical Chance * Chance of Confirming the Critical) * ([average damage * critical multiplier] + any critical hit effects), assuming all valid critical threat rolls would land a hit on the target.

However, if (keen Critical Chance * Chance of Confirming the Critical) * ([average damage * critical multiplier] + any critical hit effects) is greater than or equal to 3.5, keen is reliably coming out ahead of flaming in terms of damage.

So let's say we're using a +4 keen Scythe (19-20/x4) with a Strength of 24. It's a 2-handed weapon, so we add +10 damage from our strength and +4 from the enhancement bonus, for 2d4+14 damage (average of 19). We have a 10% chance to threaten a critical hit and, for the sake of simplicity, let's say we hit the target on an 11 or better (50% of the time).

Our estimated damage gain from keen is (.1 * .5) * ([19*4] + 0), which comes out to 3.8 damage. It's marginally better than flaming on a similar weapon (by 0.3 damage per average hit).

[Glimbur]

If you want to get fancier about it, remember that your baseline for comparison adds 1d6 elemental damage, i.e. fire or ice or what have you. Some monsters, particularly outsiders, have low to moderate resistance to many elements. Some monsters are immune to an element.

On the other side, some creature types are immune to critical hits.

So, if your campaign is Lord Shining Versus The Undead Hordes, skip keen and get flaming (not frost). If your campaign is Where Did All These Devils Come From, then keen is a better choice.

[sleepyphoenixx]

It's not worth it as a weapon enhancement (or feat) since you can get it cheap enough elsewhere and those effects don't stack.

[hymer]

@ OP: It depends. Do you have someone to regularly cast Greater Magic Weapon for you (if not, and if you deal lots of damage already, the straight increase of your enhancement bonus to-hit may well be better)? Do you have access to all kinds of magical items (such as a scabbard that makes weapons Keen, e.g.)? How many weapons are we talking about? The feat (Improved Critical) becomes more interesting if you wield many weapons at once, but much less so if you wield only one weapon, or more than one kind of weapon. How often do you encounter something that is immune to criticals? Can you overcome that immunity? How good is your weapon at crits already? Multiplying your crit effectiveness is better on crit-strong weapons. Do you have feats or abilities that make criticals more powerful?

I wouldn't take it on just any character, but there are cases when a Keen Weapon could be a worthwhile investment.

[Thrawn183]

Keen is worth a +1 bonus which, at most, can get us a reliable 3.5 damage (Flaming or similar enchantments).

Note that keen becomes less useful as our chance of confirming the critical hit decreases. Its value is (keen Critical Chance * Chance of Confirming the Critical) * ([average damage * critical multiplier] + any critical hit effects), assuming all valid critical threat rolls would land a hit on the target.

However, if (keen Critical Chance * Chance of Confirming the Critical) * ([average damage * critical multiplier] + any critical hit effects) is greater than or equal to 3.5, keen is reliably coming out ahead of flaming in terms of damage.

So let's say we're using a +4 keen Scythe (19-20/x4) with a Strength of 24. It's a 2-handed weapon, so we add +10 damage from our strength and +4 from the enhancement bonus, for 2d4+14 damage (average of 19). We have a 10% chance to threaten a critical hit and, for the sake of simplicity, let's say we hit the target on an 11 or better (50% of the time).

Our estimated damage gain from keen is (.1 * .5) * ([19*4] + 0), which comes out to 3.8 damage. It's marginally better than flaming on a similar weapon (by 0.3 damage per average hit).

This is almost correct. We need to look at the damage added by keen, which doesn't include the pre-existing critical hit chance. In this case keen only increases the critical hit threat range by one: (.05 * .5) * ([19*4] + 0) = 1.9, which is not as good as a simple flaming enchantment.

[Djinn_in_Tonic]

This is almost correct. We need to look at the damage added by keen, which doesn't include the pre-existing critical hit chance. In this case keen only increases the critical hit threat range by one: (.05 * .5) * ([19*4] + 0) = 1.9, which is not as good as a simple flaming enchantment.

This is correct. Thanks for correcting that. Don't know what I was thinking.

[Lanaya]

That being said, the swingy nature of keen can be an advantage. Flaming, frost and shock will reliably add a little bit of damage to each attack, which is nice but unlikely to have a huge impact. A keen scythe will usually have no effect, but once every so often you'll roll that 19 and confirm the critical and almost cause an instant kill. Getting the occasional free win in an encounter may be better than consistently doing somewhat better.

[Runeclaw]

Get a Scabard of Keen Edges instead.

[tyckspoon]

Get a Scabard of Keen Edges instead.

Keen/Imp. Crit is questionably worth having as an always-on property, depending on your build. I don't think it's ever worth using an in-combat action to acquire like you have to do to activate a Scabbard; if you're interested in average damage per attack or per round or whatever, you're pretty much always going to get more by using that action to *make an attack.*

[Runeclaw]

Well, it lasts 50 minutes per use and you get three uses per day. So I think you should be able to keep it up for your biggest fights of the day without giving up an actual combat action, unless you are getting ambushed.

And it's a hell of a lot cheaper than putting it on your weapon.

Of course, it only works on dagger- and sword-like weapons, per RAW.

[Greenish]

And it's a hell of a lot cheaper than putting it on your weapon.That depends on the weapon, obviously.


Alignments (both party and usual enemies) allowing, I'd probably prefer Imp. Critical and Sacred Scabbard/Blessed weapon, but Keen is pretty fun too (who doesn't like critting?), though its actual efficacy depends on a whole bunch of variables.