Ah great. I missed that. Still avery powerful ability. It is somewhat comparable to something like quicken spell or twin spell... but free, and you can cast two leveled spells, and you can mix and match and not have them the same. Even if it is just 1st level spells this is seriously good. There is nothing wrong with seriously good class abilities though. As long as the other abilities reflect it.
I really, really think this ability can be too easily broken by the feats/races/backgrounds that give you extra spells on your spell list. A level one spell slot for a twinned dissonent whispers - or a dissonent whispers + command (with a potential reaction move AND a dash action this would almost be as good as banishment for just removing some enemies from the fight).
There are some level 1 spells that scale well enough into the late game (including non concentration spells) that this can be really potent.
Ah, I see that. It does make sense.
So someone takes the Ravnica Orzov background and can get a spirit guardians with radius 40ft? Even forgetting about the damage, this much halved movement radius is obscene. This ability seems to either be pretty useless, if you just use the class spell list, or monumentaly powerful if you use the options to extend it.
I ran into this problem with my submission as well - my work-around was to provide bonuses only to the spells granted by the subclass - anything added to the main class list would not be added to the specific subclass list so wouldn't get any bonuses.
I think this is a better way to go (still need to see the detail) but likely to be simpler, slow the game down less.
Even accounting for this, I think the class is still very, very much on the strong side.
Just opening the PHB at the first class there I have the barbarian as a typical not overpowered class that fulfulls a fantasy OK.
You have some really great class abilities - like rage. The really defining one.
But most of the class abilities are unremarkable:
Unarmoured defense?
Danger sense?
Reckless attack?
Fast Movement?
Feral Instinct?
Brutal Critical?
Persistent Rage?
Indomitable Might?
Primal Champion?
You get a lot of small, incremental improvements in what the class does and one, maybe two big or scaling features. I am worried that instead of a small minority of your abilities being the big flashy ones the majority of your abilities are really powerful.
Of your abilities I would say the ones in red are of the kind of power that can define a class:
Critical Cast
Spell Sling
Fire at Will
Limit Breaker
Arcane Wellspring
Limit smasher
Limitless
Limit breaker is a bit of a borderline case - it is clearly powerful, but not class defining.
And even if we look at the subclasses I think we see a little of the same.
I would say for the barbarian that the totem barbarian is probably the most popular, so a quick look at its features:
Spirit seeker
Totem spirit
Aspect of the beast
Spirit walker
Totemic attunement
Of these, I would say you have a number of out of combat or more flavour focussed abilities (or some that are just highly situational) with Totem spirit and maybe Totemic attunement standing out as actual powerful abilities.
If we compare with just your first subclass:
Magnetic propulsion (totally transforms a number of spells, potentially very open to abuse with some options)
Magnetic leviatation - a 5-fold increase is acccessible and a HUGE difference. Yes, levitate can now move 100ft in a turn. It isn't a terrible spell to begin with but this makes it pretty damn good (again no objection to good things, it is just about keeping an eye on the ratio of good to mediocre things. But it is when you get telekinesis that things get crazy... you can move a creature 150ft potentially, and swap which creatures are moved. A melee enemy has to close with the party to do ANYthing and you can effectively keep everyone away from you or pluck someone from the distance and bring them close to murder range. Normally this would be constrained by the stipulation that you cant move anyone beyond the range of the spell... but thanks to Magnetic Propulsion that can be up to 300ft. It is another good ability. Sure, confined spaces will limit this somewhat, but it still looks significant.
Magnetic repulsion is niche, but not weak. This is an unremarkable ability.
Magnetic impact - again it depends on if inside. Dropping one enemy on another from a 150ft telekinesis move now does an extra 4d6+10 damage (assuming you have maxed Int by now), which is modest, but does add up turn after turn when its just bonus damage on a control ability.
I would also say that I think this is probably your weakest subclass (in terms of power).
I guess my worry isn't just any given ability, but the cumulative effect of multiple good abilities that synergise too well together. I think individually a lot of the abilities are great and a lot of fun and are exactly the kind of thing I would love to see on more classes, but stacked together... they just seem a bit much.
Indeed some just look like better versions of other classes abilities - like the Thermalist's Prolonged Exposure compared to the draconic sorcerer's ability. Double the types of damage it can apply to, comes at half the level, and either also costs an action from the target or does even more damage. Or the vulcanist's Lave Bender ability - compare to the sorcerer which is a bonus to one roll when you cast a spell; this is also applying to attacks but can stack multiple times, turn after turn.
I get I am being picky; I really do like most of what you have here.