I'm playing a barbarian. Another player's PC is a warlock. The warlock is constantly using the spell command on my barbarian, and it's annoying. How can my barbarian avoid the command spell's effects?
Mechanically, there are number of methods
The right way to approach the problem is talking to the player. However, your question was "how can my barbarian avoid the command spell's effects" specifically. Well, the description of the spell is:
Casting Time: 1 action
Range: 60 feet
Duration: 1 round
You speak a one-word command to a creature you can see within range. The target must succeed on a Wisdom saving throw or follow the command on its next turn. The spell has no effect if the target is undead, if it doesn't understand your language, or if your command is directly harmful to it.
Therefore, possible methods of preventing/avoiding the Command effect are:
- Kill the caster. Dead warlocks do not cast spells.
- Threaten the caster. An RP-ish way: "That's an insult! If you do this again, I'll rip out your tongue!". Keep in mind your character is completely aware of the Command spell effect.
- Knock the caster unconscious. An unconscious creature can't take any actions, including casting a spell.
- Blind the caster. The caster has to see the target.
- Silence the caster. The caster has to perform the verbal component. He cannot cast anything while gagged.
- Take the Mage Slayer feat. It gives you advantage on the saving throw and allows you to attack the caster as a reaction, but only when the caster is within 5 feet.
- Go away. Don't stay near the warlock. The spell range is only 60 ft.
- Deafen yourself. Apparently you have to hear the caster in order to be affected, despite the fact the spell description doesn't require this explicitly. Ask the DM how the spell works in their game.
- Succeed on the saving throw. There are plenty of methods of increasing your chances of a good roll. Raise your Wisdom score. Take the Lucky feat. Take the Resilient feat. Find a magic item that helps you succeed on saving throws (Ring of Spell Turning, for instance).
Less reasonable, but still valid methods:
- Become unable to understand language. The spell description explicitly requires the target to "understand your language". For instance, you "can't understand language" after the Feeblemind spell.
- Incapacitate yourself. "If the target can't follow your command, the spell ends".
- Die. - A dead body is considered an Object and is not affected by any creature-targeting spell.
- Become undead. "The spell has no effect if the target is undead".
This is Player vs Player interaction. Some tables have a rule against this. Check with your DM. Beyond that, explain to the warlock player that their behavior is reducing your fun with the game. If they are reasonable, they should stop. If they continue, they are being a jerk. No table should allow jerks. If you can get no satisfaction by talking to either DM or player, you are left with three options:
1) tolerate it
2) leave the group
I do not recommend the third, as it tends to escalate the situation and can lead to hard feelings. However, your barbarian does not have to like the warlock, can refuse to aid him in combat, fail to warn him of traps or surprise attacks, etc.
Finally, warlocks have a very finite pool of spells. If they are wasting one of their (likely) 2 spell slots on practical jokes, this will backfire on them eventually. AFAIK, there is no warlock invocation that grants command, and only Pact of the Fiend even grants the use of the spell in the first place. This is poor spell maintenance and detrimental to the party.
These are my recommendations. However, if your desire is merely to resist the effects of the spell, your options are limited. You could stop up your ears. The target needs to "understand the language" of the command, which in this case I would interpret as needing to hear it at all.
First of all, on the level of "another player keeps commanding my character to do things they wouldn't normally do and it's bothering me," is there a reason you can't talk to the warlock's player and tell them it bothers you? This is almost like a form of railroading, except instead of the DM forcing your character into situations it's another player. It's just as not okay from a RPG etiquette standpoint, and if they won't listen you should talk to your DM about it - they can probably sway the warlock's player if you can't.
In-game, though, you should have a few options. The command spell requires a wisdom saving throw to succeed. I'm sure, if this is a problem, wisdom is not exactly your barbarian's strong suit, and there aren't very many items that increase wisdom on their own. So:
If you take the Path of the Berserker, at level six you gain the Mindless Rage feature, which means you cannot be charmed or frightened while raging. It doesn't help the rest of the time, but it's something. (Edit: I have been informed by @keithcurtis that Command is not a charm effect. Whoops!)
It'd be really hard to come by, but the Tome of Insight, when read, grants you a +2 to Wisdom.
- There aren't any preset items in 5e that I can think of that would help with wisdom saving throws, but if you talk to your DM and they for whatever reason can't do anything about the player outright, you could see if they'll homebrew something like that and drop it in as loot. Suggestions might be something that grants advantage on wisdom saving throws, or maybe just a +1 or +2 bonus. Once you come by it you can get other players to let you use it by explaining that it would be really bad for them if you're controlled by an enemy, and this item will help that not happen.
Beyond that, I will reiterate that you should talk to the warlock's player outside the game. They may think that this is a fun dynamic between your character and theirs, and not even be aware that it bothers you.
Command only allows single word commands. With a single word, you can only specify an action, not a target. So next time the warlock commands you to "kill" "charge" "attack" or whatever, you're completely justified in targeting the warlock :). ("He made me do it! :) :) ) In any case, after the single round duration expires, you're free to... forcefully express your displeasure... with the warlock. Or keep disturbing him when he's trying to rest to relearn his spells :). Or just rip his head off and use it as a football :).
Other answers have already addressed that sometimes in certain playstyles what the warlock is doing is off limits. This answer will assume you are in a game where that's not the case, and where PvP activity is totally acceptable.
Become extremely attached to your beliefs
Command doesn't work if the command directly harms you. Arrange yourself (by which I mean the interior state of your soul) such that acting against your beliefs constitutes direct emotional harm. Use the opportunity to decide what things you really care about, and to remove the obstacles in your life that lead you to sin against them, especially sins of omission. If you possess the spiritual state that guards against sins of omission, commands to sin against your ideals will constitute direct harm.
This method of avoiding the effects is superior to all others, because it provides an opportunity to develop your character and costs no mechanical character resources.
In addition to bettering yourself to prevent this kind of problem in the future, you should punish the Warlock for their bad actions. What constitutes an appropriate punishment depends on the nature of your in-character relationship and those with the rest of the party. Unlike in previous editions, however, you can possess the might necessary to enforce your punishments against the full-caster's will despite not being a caster yourself; don't be scared just cause the warlock can rearrange the universe. Your party less the warlock working together should still win a fight, as long as there's at least two of you. That's not to say that you need to fight the warlock, but the fact that you conceivably could strengthens your ability to impose penalties against them.