What is an equivalently powerful replacement spell for the Yuan-Ti's Suggestion spell?

Question

I'm currently running

Tomb of Annihilation

and there's a lot of Yuan-Ti the party is about to encounter.

My party has had a lot of contention and pain-points with the Suggestion spell, and it appears to be a hard spell to tie down RAW, as it is subject to a lot of contextual judgment calling and opinion based reasoning. I'm hesitant to even ask this question because the spell itself is primarily "opinion-based", and it may be closed due to its nature.

Also, every Yuan-Ti can cast this spell innately.

I don't want to deal with this potential headache. What are my options for a balanced, suitable replacement for Suggestion based on these criteria:

1. The spell is also 2nd level or lower.
2. The spell deals no direct physical damage upon its casting.
3. The spell is related to either the Enchantment school of magic, a charm effect, or some other mind-altering effect.
4. The spell must be useful in a combat encounter (for example, having direct language relating to actions taken in combat, or hostility).

Spells that keep with the theme of the Yuan-Ti would also be the most preferable and hopefully the above criteria narrow down the search to objective guidelines that do not produce subjective, opinion-based answers.

Answer 1

There are a few options from the school of Enchantment that should keep the theme.

I am listing 1st-level spells first. I would recommend allowing the Yuan-ti to cast them at 2nd level to keep the power approximately the same as Suggestion.

• Command cast at 2nd level - this will target 2 characters, but will only last 1 round.
• Charm Person cast at 2nd level - will also target 2 characters, but they will have advantage on the save if they are fighting the Yuan-ti. This may be the most on theme for Yuan-ti.

2nd level spells:

• Enthrall - this spell might allow one Yuan-ti to act as a distraction while others sneak up on the party.
• Crown of Madness (PHB, p. 229) - although it is also 2nd level, this spell is slightly more powerful as it would allow the Yuan-ti to each take control of one of the PCs.
• Calm Emotions - This can be used either to temporarily end hostility from enemies or suppress charm/fear effects in allies.

Answer 2

Keeping the table happy

The important thing to note here is that casting spells that take away player agency is almost always going to be a problem. The most important thing is to not present your players with something that will go awkwardly or make them feel like they aren't in control.

Don't put them in a position where you are taking their player agency away. Give them an opportunity to do some interesting things with roleplaying charmed, but they shouldn't feel like you are owning their characters and their choices. If you do use enchantment spells that may do this (suggestion, charm person, command, crown of madness, etc), you need to be really careful about how you do it. Command is a bit simpler because it's just one turn, but you've taken your player out of play for that turn. The others you need to be very careful with as well so as not to think you are in control of their characters.

Dangers of Suggestion and the like

These spells aren't dominate person. Even suggestion stipulates:

The suggestion must be worded in such a manner as to make the course of action sound reasonable.

If you can't make a reasonable case, then what you're asking isn't reasonable. Coercion isn't reasonable. Reasonable is something that the character would say to themselves "Yes, this action seems completely reasonable for me to do as if I was choosing to do it myself."

And you've only got a sentence or two to make your case. It's not easy! And that's where the spell is limited.

Here is an excellent Q&A on figuring out what's a reasonable suggestion.

Suggestion may be perfectly fine to keep with your Yuan-Ti, but you may need to approach how you use it differently.