Two members of our party recently came under mind-altering effects (not sure exactly what it was, maybe Suggestion, but it involved failing a Wisdom save), causing them to attack the rest of the party. I'm not sure what was told to the Rogue, but I know the Barbarian was told that he was in danger, and needed to attack everybody, including members of the party close by. (I don't have a direct quote, it was a few days ago.)
This was extremely detrimental to the party, since it was our Barbarian and Rogue who were affected, meaning that our tank and main damage dealer were both turned against the party in combat.
This got me thinking: what actions can our party take (both preemptively and in battle) to counter or prevent Suggestion?
Our party composition (all level 20):
- Barbarian (Totem of the Bear)
- Wizard (Evocation focused)
- Druid (Shapeshift-focused)
- Rogue (Assassin)
- Bard (College of Lore)
Preemptively, I was thinking about perhaps plugging our ears with cotton or something else, though this would surely give us some sort of disadvantage on auditory checks, and I'm not sure if this would even counter spells like Suggestion (I'm not familiar with how functionally these mind altering spells work - I've only played melee characters).
In battle, the only thing I could think of on the fly would be to use the Bard's Cutting Words ability, though I'm not sure if it would be effective since presumably the monsters would be using spells, which would not fall under the "Attack roll, an ability check, or a damage roll" restriction of Cutting Words.
Thus more generally, how can we as a party prevent Suggestion from succeeding? Are there spells that would prevent Suggestion from working, or magical items which would confer relevant status immunities? Are there preemptive strategies that we could have taken to reduce the effectiveness of Suggestion, or to nullify it entirely?
I feel like I am missing something strategically regarding how to counter Suggestion, so any recommendations based on experience, RAW, RAI, or otherwise will definitely be appreciated.