Part of an ongoing (if occasional) series of D&D 5e Rules notes.

Everybody wants to be the hero.

Every character wants to be the one to land the killing blow.

But sometimes, it’s better to ask for — or give — some help.

A lot of player characters, especially in the support classes, have spells that will enhance other people’s rolls, which is very cool.

But in a sense, everyone has that ability, through the Help action (PHB 192):

Helping with Ability Checks

You can lend your aid to another creature in the completion of a task. When you take the Help action, the creature you aid gains Advantage on the next ability check it makes to perform the task you are helping with, provided that it makes the check before the start of your next turn.

This mechanic is explained more under “Working Together.”

Sometimes two or more characters team up to attempt a task. The character who’s leading the effort–or the one with the highest ability modifier–can make an ability check with advantage, reflecting the help provided by the other characters. In combat, this requires the Help action.

A character can only provide help if the task is one that he or she could attempt alone. For example, trying to open a lock requires proficiency with thieves’ tools, so a character who lacks that proficiency can’t help another character in that task.

Moreover, a character can help only when two or more individuals working together would actually be productive. Some tasks, such as threading a needle, are no easier with help.

So it’s not enough to Help by holding the thief’s tool kit while they are picking the lock, or shouting encouragement to the guy trying to climb a cliff wall. You have to be able to do the thing you are assisting, and describe how you are helping.

What is the difference between Help and Working Together? The former is an action type during combat. As GM, I might be a little lenient on combat-setting “how are you helping?” actions, e.g., “I stand there, looking menacing at the attacking goblins, while screening the Rogue from view as she tries to pick the lock so we can get out of here” (you’re not directly assisting with the lockpicking, but you are sacrificing your action to let the Rogue focus on their without worrying about being stabbed = Advantage!).

Helping with Combat Rolls

More frequently, Help is applied directly to combat situations, as well.

Alternatively, you can aid a friendly creature in attacking a creature within 5 feet of you. You feint, distract the target, or in some other way team up to make your ally’s Attack more effective. If your ally attacks the target before your next turn, the first att⁠ack roll is made with Advantage.

This might be a way, for example …

• If you know the opponent has resistance or immunity to your flaming sword, maybe you can be more effective Helping the other fighter with a cold-based weapon.
• If you know the opponent will be hit harder and more effectively by an ally (because of the nature of their weapon, or just because they have a huge damage bonus on strength), you might consider whether its worth effectively giving up your attack(s) for them to get an attack at Advantage.
• While a Rogue will be automatically able to Sneak Attack if you’re within 5 feet of a target, giving them Advantage to deal out that ton of damage they’re about to roll may be tactically the best course.

Note that this not a matter of Reach, but a 5 foot limit. So if someone with a Glaive wants to provide Help, they need to step in to 5, not hang out at 10 feet.

Also note that Help is just for the first attack. That makes it somewhat more useful at lower levels, when you are only sacrificing one attack to make that happen, and the bonus is going to the only attack the attacker has yet.

Also note that you are Helping a specific attacker. “I am going to help the Rogue with their attack on the goblin I’m next to.”  If the Paladin goes after the goblin first, they so not get the Advantage bonus. And if the Rogue decides on a different target, the Help has been wasted.

Help is also usable to assist with spell attacks, granting advantage on any sort of spell attack roll against that target.

Finally, Help is an action frequently assigned to familiars and animal companions and the like — these often cannot attack, but can be commanded (or urged) to “Help the Fighter!” (“Bark bark!”)

As a GM, I like to encourage players to give me some idea of what they are doing to “help” in this way. “I wave my hands and attract the orc’s attention.” “I try to keep her sword busy clinched with mine.” “I shout, ‘Ashtuk, is that you?'” No mechanical effect is applied except the Advantage it provides, but it’s nice color regardless.