Diablo III- Skills Article LXXXVI: The Monk, Mantras- Mantra of Conviction

Mantra of Conviction (50 Spirit): For the next 3 minutes, all enemies take 12% more damage while within 20 yards of you.  For the next three seconds, all enemies take 24% more damage instead while within 20 yards of you.  You can only have one Mantra active at a time.

The only Mantra that doesn’t specifically aid allies, Mantra of Conviction is almost certainly going to be your Mantra of choice if you’re fighting alone.  Further, since it debuffs enemies instead of boosting allies, you may still find yourself using it when you’re in a party- and there’s nothing wrong with that at all, as the effect remains both strong and useful no matter what’s going on around you.  A good way to get in additional, reliable damage without having to lean on enemies striking you- as long as your allies stay nearby so they can hit things that are near you.

Overawe (50 Spirit): For the next 3 minutes, all enemies take 24% more damage while within 20 yards of you.  For the next three seconds, all enemies take 48% more damage instead while within 20 yards of you.  You can only have one Mantra active at a time.

Pretty straightforwards- deal even more extra damage to everything.  No party’s going to hate this, so if you use Mantra of Conviction, this is a good reliable go-to rune that can be used (and abused) at any level.

Intimidation (50 Spirit): For the next 3 minutes, all enemies take 12% more damage and deal 10% less damage while within 20 yards of you.  For the next three seconds, all enemies take 24% more damage instead while within 20 yards of you.  You can only have one Mantra active at a time.

The most reliable combined offense-defense Mantra available, Intimidation works best when you can ensure that enemies stay within its range- Cyclone Strike is an invaluable tool here, as while its default range is the same as the Mantra, it brings things to the very center of that area, forcing them to take a long run through it if they want to escape the effect.  A straight 10% reduction in damage isn’t the strongest defensive effect available, but it’s universally applied, so there’s really no way around it once you’re near the enemy in question.

Dishearten (50 Spirit): For the next 3 minutes, all enemies take 12% more damage and have their move speed slowed by 30% while within 20 yards of you.  For the next three seconds, all enemies take 24% more damage instead while within 20 yards of you.  You can only have one Mantra active at a time.

A very nice tool if your allies like slowed enemies, Dishearten helps you keep things together for area attacks, keeps enemies from running away as easily, and just sort of generally impairs things on top of making them hurt more.  A very good tactical choice if that’s what you need for your party.

Reclamation (50 Spirit): For the next 3 minutes, all enemies take 12% more damage while within 20 yards of you.  For the next three seconds, all enemies take 24% more damage instead while within 20 yards of you.  You can only have one Mantra active at a time.  When you or an ally strikes an enemy under the effect of this Mantra, that character has a 30% chance to heal an amount of Life based on your level (279-341 at level 60).

This isn’t a terribly useful rune.  While it’s true that your entire party will love dogpiling enemies that are near you when Mantra of Conviction is active, the healing from this rune is very small, and with less than a 1/3 chance of happening on any given hit, it’s simply not reliable anyways.  You have better options for your rune on this skill- if you’re worried about your allies falling in battle, choose Intimidation.

Submission (50 Spirit): For the next 3 minutes, all enemies take 12% more damage and take 12% weapon damage as Holy Damage every second while within 20 yards of you.  For the next three seconds, all enemies take 24% more damage instead while within 20 yards of you.  You can only have one Mantra active at a time.

Submission grants you the most powerful damage aura in the game- not because of the amount of damage it does, but because of the area it effects.  At 20 yards, this aura will steadily injure huge numbers of enemies as you move in and then finish killing them, and while you can’t really rely on it to actually kill anything on its own, it compounds its own damage boost with actual damage, steadily weakening things in a way that will virtually always be useful.  As with any area effect, it essentially gets weaker the fewer things are present to affect, so you should probably switch to something else when fighting a boss.  Against more common mobs, though, this is gold.