Well the poll on my page was clear, and the Charger revision is going back to the drafts for awhile.
You terrible people.
All's well though, spellcasting is one of my favorite topics when it comes to games in general. Now, I love magic in tabletop RPG's in particular because there's such a variety of actual spells. Far too many they could get a game like sky room, there's just too much programming and development of assets that would go into developing 1/10 of the spells D&D has (that's not including situations that would involve their application, though most are combat focused so it's layered with other things).
However if you're like me, you might find spellcasting and D&D a little stale after a while. You're constantly looking up spells that don't have the concentration tag's you can layer some active effects, combats only last three or four rounds, and there's all the spells you can't really justify casting over something else. There may be a situation one in a million where casting wall of sand would aid the party in combat. Perfectly reasonable assumption. However, there will never be a time in which casting wall of sand is a better tactical option than casting haste.
So, my first choice for editing spells within D&D is screwing around with the concentration tags. Now, I've already gone into elsewhere what my current system for managing concentration is. For those of you not quite looking to rip off that band-aid yet, no worries, I'm going to try something a little different here that hopefully exposes the process.
We're going to run down a 5 step plan for determining whether you can take concentration off a spell without breaking the game. There's plenty of obvious spells to choose from, but I'm going to see if I can't run down a list of more difficult choices (can't grow if you don't challenge yourself).
1. Compare the spell to haste.
Haste isn't actually the linchpin here but it's a useful example. Chances are, if you play for a year or more, certain casters have a signature spell. It's the best, the party moves around it, it's the first suggestion someone makes when they want to solve an issue, it's the first thing someone casts in combat. In the game I'm currently playing, literally every player has some sort of martial competence. On top of that, we find ourselves kited often (mostly bosses fleeing from the raging half-orc with two greatsw-ALL HAIL KAINO THE MOUNTAIN) so the speed boost is gravy. Any other concentration spell I cast is weighed against the speed and damage boost 2 or 3 of my party members are receiving at that time, so it's rare that I drop anything else on the field. Spike growth COULD be cool in some situations, but I rarely have the excuse for it. For these reasons, haste is my go-to.
2. Evaluate the opportunity costs of the spell.
What happens when a character drops concentration on another spell to cast this one? How does the battlefield change? Is it more valuable to maintain concentration on a hold monster or fog cloud then switch to this one? Will it see any use? If you drop in this instance the concentration tag, does it displace the other spells? Obviously if you remove concentration from the spell they can deploy the effect alongside a concentration effect.
Let's say we've got a spell, single target to keep things simple. It doesn't deal any damage but incurs a pretty hefty status affect. Not something that hurts a creature's action economy, just makes it worse that using the actions it has available to it. That spell sounds pretty fun, and it is! It has to pretty hefty downsides though. It offers a saving throw for the effect obviously not bad enough itself, and that save is Constitution based. Monsters tend to be decent at Constitution and strength saving throws. Next, the spell offers a repeating save. The spell can fail well before it would naturally end or even before you take damage and may be feel concentration check, even if the spell originally succeeds. For arguments sake, let's make the spell second level quite a few second level spells match the sort of design.
Now the spell isn't useless by any stretch of the imagination, it's still pretty powerful. Do we add the concentration tag to it? I'd say no! The restrictions placed on the spell are significant, and the spell's benefit isn't something that takes the enemy off the board. It doesn't deal damage, and it has a good chance of failure even if the spell succeeds at first. If you add concentration to this spell, it's not going to be terribly impressive. So unimpressive, that it gets moved from a "nice in-pocket spell" to "right in the never-cast list with wall of sand".
So, we do not add the concentration tag to such a spell. If said spell has that tag, we remove it.
This spell exists, by the way. It's Blindness/Deafness, and it's great for minibosses and clutch moments when I'm playing a character focused on battlefield control.
3. Compare the spell to other spells of its kind.
There's a cluster of 2nd level spells that really overlap in their utility and purpose, mechanically and thematically. Suggestion, Crown of Madness, and Hold Person (that last one might seem odd but I promise it's supposed to be there) all serve to diminish or cut out action economy in some fashion when it comes to the enemy.
Are your players going to ignore spells similar to the one you've selected to change? Is that an indication those other spells are in need of a fix as well? Or are you just boosting a spell to be too powerful?
4. Consider any exploits that result from changing it.
This step in the process of editing the spell is particularly relevant given the tag have chosen to use as an example. After all, concentration is fifth editions design Band-Aid on too many spell effects. So naturally, making your mechanical change in this area exploit – proof is especially necessary.
It's almost like I plan these things.
Changes to debuff spells are especially in need of attention. Stacking multiple conditions on top of one another can create a much faster downward spiral for your monsters. Creature fails wisdom save, creature has a condition that makes it automatically fail dex and strength saves, casters start throwing those spells at the creature, tensions rise, the DM flips the table. Avoid this.
Don't engage in theory crafting; honestly think about how your usual combats play out. Mine tend to go about 3-4 rounds, and the players tend to get surprised more often than they do the monsters. I wouldn't think about what would happen if the cleric had 6 rounds of not taking damage, total preparation, no restrictions on line of sight, no risk of the monsters overwhelming him, etc. That situation will never play itself out in the game, not even by accident. Does the caster become a higher value target for intelligent monsters? Does the caster somehow make themselves more difficult to hit or take damage with the spell? Do the effective damage reductions also restrict their ability to affect the battlefield? Play out the situations in your head, or just take some 1" grid paper and literally play out the situation on paper. Not enough DMs do this, in can seriously benefit your design decisions.
5. Evaluate whether toning down the spell may be worth the tradeoff.
There are two easy ways to tone down spells that are normally concentration. First, add a repeating save. There are few concentration spells that last for something like a minute and do not offer a repeating save. Spells of these sorts are usually justified in having the concentration tag. You might want to remove it anyways for whatever reason, so a good way to tone it down is to inflate the chance of the spell's failure. Pretty simple, right? Now some spells have a one minute duration and already offer a repeating save. If you want to remove the concentration tag from that spell, your easiest option for diminishing the effect is hard capping the duration. Make the spell last until the end of the casters next turn. It's a hefty penalty, but it's a nice trade-off. Now, what if you've encountered a spell that already caps the effect at the end of the casters next turn and has the concentration tag? More likely than not, you found a poorly designed spell. But if some miracle such as spell exists and deleting the concentration tag would make it unbalanced, simply increase the minimum level at which it must be cast. In fact, that change is relatively easy to institute to begin with and perhaps easier to remember.
This stage of the process is what I'd most recommend consulting with your players. As the adage goes, if it ain't broke don't fix it. After going through the previous steps, you may find a proposed mechanical change is best in your eyes balanced by diminishing some aspect of the spell. There are a variety of ways to do this of course, but I'd like to note that this step of the process is most likely to step on your players toes. Now, don't try to avoid that while going through this process up until this point. You would to plunge yourself into the mechanics, the math, the way your change plays out of the table. This plenty of opportunities for somebody to be mildly inconvenienced by a change you made; you need to ignore those thoughts while testing things out, or a else slow (worse yet, stall) your progress.
Once you get to this point, feedback is helpful! Making the design process collaborative for this sort of thing in the early stages can be difficult. It's far too easy to shoot each other down before getting things on paper. And since prototyping mechanic for a tabletop game is noticeably easier than prototyping for something like a videogame, the potential payoff for ignoring everyone else to get the idea established is far too high to resist. So, ask your players! Ask whether this will step on any of their toes! They will be best equipped to see if this will have any immediate or obvious detriments to their enjoyment of the game.
Note: Sorry for a lower quality here, I had a really excellent 2-5 point list buy didn't save changes, so a lot of this is re-hashing things I'd already written down.