Mass Suggestion, like most of the Mass spells, takes a thing and both improves it and multiplies it. In this case, you can control up to twelve creatures at once with a simple suggestion. It can be as basic as “don’t move” to neutralize up to twelve enemies at once, or as complex as “be my personal staff for the day”. So long as it “sounds reasonable”, they’ll do it!

Arms of Hadar is a spell I want to take, and want to see players flexibly use, but it falls victim to the spell murderer that is pact magic.

In specifically deadly encounters, Aura of Vitality can net your side a tremendous action advantage that can turn a loss into a win.

Intellect Fortress is an unbelievably boring effect that you can’t reliably fall back on, and when you can, it sometimes will just do nothing anyway. The name makes it sound cool, but at most tables, this spell is horrendous.

Nondetection is a non-spell. It's a 3rd level spell tax DMs can ask players to make, or a DM tool to simply say no when the players attempt to spy on the villain. It’s a tool that has so many flaws and workarounds it feels horrific to have to use, and even worse to stumble into with your own divination magic. 

Death Ward is a rare case where some subclasses getting access to it completely change the functionality. Clerics and paladins can get a fine enough amount of value from a death prevention tool for a 4th level slot.

The core issue with Insect Plague is in its inflexibility. You’re stuck with a single zone dealing 10-20 damage each turn to any creature within the space, which can be solid. With it applying at the end of turn, not start, though, it basically forces creatures to move.

What Wall of Fire typically does is bar large quantities of weak creatures for a minute. DMing encounters opens up a lot when you start to incorporate alternate objectives and different methods of grouping monsters; using swarms and waves can make Wall of Fire FEEL amazing as group after group of mindless undead throw themselves at a wall they can’t possibly get through.

Wind Wall is a large area 3d8 bludgeoning damage spell that prevents ranged attacks from passing through. For a 3rd level slot, you could be casting Fireball, dealing twice the damage in a sizeable area, so baseline, you don’t want to be casting this just for the damage.

There are two main use cases for Dream: you need to talk to somebody you know, or you need to deny the rest of somebody you hate. Both these cases can occur, but are hyper dependent on the campaign.

Black Tentacles takes the silliness of D&D and runs with it. Conjuring a squirming mass of ink black tentacles that writhe about restraining and smacking anything they touch is the exact kind of nonsense I expect when I’m making things up with my friends.

Dominate Person: at 5th level, this spell brings a world of complications and moral nightmares to play. The spell is at its best when used creatively out of combat; control over a very specific person at the right time can change the course of a campaign.

Antimagic Field is a Hail Mary, the kind of spell you only cast when you need a miracle. If you can cast an 8th level spell, you can conceivably also cast 7th level and lower spells and have epic magical equipment. This spell requires you relinquish all of these options when you cast it.

Arcane Hand is in my top ten favorite spells. It rewards being built around, but doesn’t require it, offers a flexible tool in encounters, and while it’ll thrive in specific encounters, isn’t useless in any. If you’re going to be concentrating on one spell, you won’t be disappointed with Arcane Hand.

Arcane Sword is exclusive to Bards and Wizards. It creates a sword-like force you can fly around and stab things with as a bonus action. One small hiccup though; it’s a 7TH LEVEL SPELL.

For that spell level this sword best be vorpal, invulnerable, cook you dinner, and pay off your mortgage.

More than most other spells, Astral Projection can create this tension and rip players out of a game that is just about to reach its conclusion. If you’re the player getting access to Astral Projection and you think you’d love to take it, talk with your DM about it first.

I can’t recommend playing in games where Private Sanctum is practical, just like I can’t recommend playing in games where Nondetection is a must. These spells exist to help obfuscate villains, and clearly to me aren’t meant for practical player usage.

Chain Lightning is just always going to do 10d8 damage to up to four things that are kind of close. It has a higher power floor, but a lower ceiling. I expect effects that last huge durations, or instantaneous effects that have a bigger impact on the current fight than "a bunch of damage" by this point.

Clone exists for players who lack access to life granting magic from their allies and lack a means of acquiring it from another source. Players who want to be extra sure that if all their friends die before them they'll live to tell the tale might take it, but even then there are better spells to fulfill that role.

Commune with Nature offers a unique method of information gathering that is notably distinct from its similarly named Commune brother. It takes activities that would normally require skill checks to perform over a longer time frame and simplifies it out to three facts in just 1 minute.