This spell is more powerful than almost any other spell in 5e, and thus should not be allowed in its current state

With the exception of wish, this might be the most powerful spell in the game if implemented the way you have it right now. If you had to pick a spell level right here and now with no modifications make it 9th level because that is the highest that 5e goes so far. However, I think this spell goes beyond the power of basically every other spell and thus should be changed or removed from the game. Some reasons for this are as follows:

It only has one save to literally defeat an enemy completely

Imagine your PCs fighting against your BBEG. Each person can cast this spell every turn with no downsides. If there is a bard in the party they can even make it more likely that the creature fails. If the BBEG fails and is alone the PCs won the battle. After the BBEG is unconscious, the PCs can cast it continually to make BBEG keep failing the save and essentially unconscious forever.

Compare this to the 8th level spell power word stun:

A creature you can see is stunned if it has 150 hit points or less. Otherwise, nothing happens. The target can make a Constitution save at the end of its turns, being freed on a success.

This spell has multiple limitations to it including a HP limit, and a save at the end of each turn to wake up and it is still a very powerful 8th level spell. Your spell is currently much much more powerful than this.

It has a short casting time

Imprisonment is another spell (9th level) with a somewhat similar effect, but arguably this spell is even more powerful than it.

As one of its effects imprisonment has slumber which says:

The target falls asleep and can't be awoken. The special component for this version of the spell consists of rare soporific herbs.

However, it has several limiting factors. The main one is that imprisonment has a 1 minute casting time. This makes it very difficult to cast in battle (that is 10 full rounds of doing nothing but casting the spell) and thus less likely to be used to completely shut down an opponent in the midst of a fight. The spell also requires very expensive and rare components to cast and also has multiple conditions that can end the spell.

It requires a very specific type of healing to reverse

In the example above, even if BBEG is not alone they need allies with very specific restoration magic to help (and a PC with counterspell could even mess up this way to help). If none of their allies have restoration magic, they might as well be alone because there is no way for them to help. In 5e similar spells and effects generally have other ways to reverse them going from minor (using an action to wake something up) up to major (dispel magic, wish). Combined with only one save the fact that the only way to reverse this is specific magic makes this extremely potent.

Even non-spellcasters can cast it

In its current state this "spell" is not really even a spell since it can be done by non-spellcasters. This makes this spell incredibly powerful beyond even any other listed spell. You have to take an entire feat just to get a couple low level spells. Gaining access to this uber-spell without any kind of requirements is insanely overpowered.

It can be spammed infinitely

Casting this spell doesn't take any kind of resource (like a spell slot) or limits (like times per day), so there is absolutely no reason for someone not to try to cast this each turn. Why try and do anything else when you have such a powerful ability with no cost?

This ability needs some serious fixing

As written, this ability is out of the realm of any other feature in 5e. Some of the bullits above are not overpowered on their own, but when you take them all together you get a feature that is incredibly powerful.

You need to make some serious changes to it as soon as possible to correct the issues I have laid out above. Even with limits, this ability is likely going to be incredibly powerful.

As it is now it now this ability is literally game-breakingly powerful.

Almost

The class is fairly well written and shows signs of editing. Most of the problems left with it are stylistic textual errors any experienced player or GM will have no trouble correcting and the authors probably didn't notice existed (e.g "You can cast animate dead" but it needs to say "... and it is a Summoner spell for you", Major Magic should recharge when you take a long rest, not the minion, it should say you can only have one minion at a time, etc). The remaining serious issues I see are:

• Forging is broken. You don't get proficiency with Smith's tools (or any other artisan's tools) and the class has no tool proficiency and that's dumb. More pertinently, the subclass gives you as many or more traits and abilities as any other subclass at every level.

• The class is only balanced for 4d6 drop one stat play. Otherwise the minion's base stats are too good.

• The minion has too many hit points. It's fine at low levels, but at high levels it will be a serious problem, especially since it gets them all back more or less every fight.

• Blood Transfer can function as a ritual cure spell, which otherwise does not exist in 5e. This out-of-combat healing is beyond anything else seen in the system. This isn't necessarily a problem, since it helps the minion not outshine other frontliners in the party since they also heal to max between fights now, but that's still a problem for balance

• Rapid Summon is a serious problem. You can summon a new minion with every action instead of taking 10 minutes. That means unless your minion dies in one round, you can restore it to full health if you want.

• I'm guessing the minion moves as you direct with no action cost to you? That could definitely use stating.

• You get extra ASIs. Those are for rogues and fighters, MAD classes with no inherent spellcasting. Why does this SAD class, which has inherent spells, get them? It shouldn't, and should instead have the normal 4/8/12/16/19 ASIs.

I think it should be fairly easy to solve these problems, though. The most important change I would make would be to make creating the minions expensive, so that players are incentivized to not reforge the minion into a completely new being after every fight. I would probably give each house a different cost, to help with the flavor of the minions being created in different ways:

Necromancers: 1 humanoid corpse per hit die. You can use beast corpses instead but it takes an hour instead of 10 minutes, and you can't use Rapid Summoning to lessen the time if you use Beast corpses.

Marionette: 10 lb/ hit die total of wood, clay, wax, and cheap dyes

Forge: 10 gp/ hit die of rare metals

Madness: two or more live beasts or monstrosities whose HD add to exactly the desired total. You can use dead beasts or monstrosities instead but the ritual takes 2d4 hours instead of 10 minutes.

The costs themselves are spitballed and should not be taken as serious suggestions. The point is that, by adding a non-trivial cost though not necessarily in gold, you limit the ability of summoners to use their summon as a freely replenishable bag of hp. They still can summon a new creature with 10 minutes of work and thus be awesome at summoning, they just have a reason to not do that all the time and to keep their minion alive and resummon it instead of a new one. This also fixes Rapid Summoning because the 10-minute timer is no longer the supposed balancing feature against creating a new minion.