what if you use this as a 9th level spell, to create three wights, each of which could have 12 zombies under it's control, then used animate dead at the 8th level, which is 11 zombies/ skeletons. you'd have 47 zombies, which is a lot. you won't have any more 8th or 9th spell slots, but still. it can become even more if you cast finger of death frequently. (btw, I don't have any rulebooks other than basic rules, can you have even more undead?) It's probably a stupid idea, but hey, why not? Also, I checked a few other spells, none of them actually worked bc you couldn't retain control for long, but you could technically cast awaken a bunch of times. 

EDIT: By the way, yes, you would need to be lv 17 to do this, and this army is only medium difficulty for a group of four lv 17 characters, and you'd probably be facing stronger foes... but then again, you would still have a bunch of adventurers that aren't casting anything, and can attack the enemy. what if your party had, say, two casters, and they both did this? Or four casters... could 12 wights and 188 zombies beat a lich?

If you use this with Wish, I don't think you even need the corpses; it just becomes a really nice permanent summoning spell.

Yeh but this move can't beat a deathknight

Boooo, get off the stage!

Three CR 1 creatures is pretty meh for a 6th level slot, IMO. And two CR 3 creatures for a 9th level slot seems rather underwhelming.

Quote from Folamh >>

You can use level 6 slot to maintain control of the wights that you create with your level 8 and 9 slots.

 No, when you cast at eight level you can create or reassert control of two sights. Casting it at 6 is control/create ghouls only

This spell could be a villain's deadman trigger, heroes coming to visit? Command your undead to walk into the orphanage/non combat allies houses/ center of market square, or anywhere innocent weak non combatants that the heroes care about are.  Tell the mighty heroes that they may end you, but in X amount of time (hopefully less than it takes for the heroes to get to the location) a number of innocents will be horrifically slain unless you go there and reassert control over them

(one clay pot filled with grave dirt, one clay pot filled with brackish water, and one 150 gp black onyx stone for each corpse) it seem to implied that you dont need to consumes the onyx so the common opinion about that.

Quote from Yselieg >>

If you use this with Wish, I don't think you even need the corpses; it just becomes a really nice permanent summoning spell.

The corpses are not material components of the spell, they're the targets of the spell, so Wish does not allow you to summon undead without corpses. There is however a spell for that.

Quote from eRaz0rHead >>

Three CR 1 creatures is pretty meh for a 6th level slot, IMO. And two CR 3 creatures for a 9th level slot seems rather underwhelming.

The advantage here being that it's not a concentration spell, thus there's a very short list of ways to mess with the spell after the fact and whatever you create lasts until it's destroyed. That's a pretty significant advantage over most of the high level Conjure spells, where one good Dispel Magic or blown CON save is enough to make whatever you called up vanish at best or more often turn on you. Also, take a look at the summoning spells. That's about as much total CR as they're inclined to give you at a time, carte blanche.

Would a wight raised by this spell have a longsword and a longbow. It doesn't seem that every pile of remains you find would have these weapons handy...?

Realistically you would have to provide the weapons since this spell just animates the bodies, but by the time you're getting wights you're casting this at 8th level and it already calls for a 150 gp per head investment; it's fine to handwave it for convenience.

What happens should a person not recast the spell with undead alive?

9th level spell slot + 8th level spell slot = 5 wights

5 wights + peaceful village -> 12 zombies under each wight =  an army of 60 zombies and 5 advanced lieutenants

Boon of high magic lets you either keep a slot free or ...

3 more wights

Max. 96 zombies with your top spell slots locked down, now all you need is lichdom and casting finger of death whenever possible

Bonuses with other undead spells let you create a grand total of >100 zombies + advanced undead.  This action economy has quite a large gdp (gross damage output) Slap on the necromancer's 14th level ability to take control of undead and the possibilities are endless, like your hoard

Quote from KaptainKittens >>

If you animate a wight with this, can the wight still create its own zombies through its life drain attack? So you could potentially have 2 wights under your control, each of which has up to 12 zombies under their own control.

 Yep! Every undead army needs some lieutenants/middle management.

Quote from eRaz0rHead >>

Three CR 1 creatures is pretty meh for a 6th level slot, IMO. And two CR 3 creatures for a 9th level slot seems rather underwhelming.

 You don't understand what wights can do. Whoever they kill turns into a zombie that the wights control, which you control. At level 20 for wizard, you have 2 8th spell slots and a 9th. This means you can make 7 wights, long rest, make 7 MORE wights, tell them to murder a town, gain 168 zombies, and rinse and repeat. Undead have low CR because they are just cannon fodder, there ment to be expandable. If you could make cr undead with 10 or higher with just one spell, there would be no opposition, and you might tick off the DM.

using this spell would you be able to create other undead with similar CR's as the ones in the spell description? For example, instead of raising wights you wanted to raise a Karrnathi Undead Soldier.

People say the mummies are weak but they can attempt to frighten things as part of their Multiattack.

The save DC is Low at 11, yes, but they can do it without cutting into their attacks, and if the target rolls a 6 or below (unlikely but possible), they get paralyzed as well. Additionally, their attacks do 20 damage on a hit, or 40 per round combined with a default to hit of +5. For comparison Psychic Scream does 49 damage average.

Additionally their fists can inflict Mummy Rot, which prevents the target from healing until manually removed. That can be extremely powerful in certain cases, such as if you’re fighting an Archpriest who can  heal themselves or their allies to full easily with Mass Heal, or, ironically enough, when fighting Vecna, because his teleport healing provides him with so much of his survivability. 

Granted, legendary resistance can prevent both Mummy Rot and Dreadful Glare, but if your enemy blows a legendary resistance on one of your mummies’ abilities, that’s a win in my book, especially if you created the mummies with your 9th level spell slot from yesterday.

Furthermore, consider that Cleric has zero damaging 9th level spells (same for 8th level spells if you exclude Earthquake, which is weird for damaging creatures). Yeah you can upcast lower level spells, but most damaging spells don’t scale very much in damage, especially percentage wise from 7th level to 9th level (notable exception is Inflict Wounds for Death Domain cleric, because it works with Touch of Death).

Anyway, thanks for coming to my Tut Talk.

Quote from WildCat2020 >>

using this spell would you be able to create other undead with similar CR's as the ones in the spell description? For example, instead of raising wights you wanted to raise a Karrnathi Undead Soldier.

 That’s entirely up to your DM. Ask them.

Personally, I’d allow it in most cases as long as the undead you raise isn’t too OP.

Don't forget you could always come to an "arrangement" with the Wight, that you will give it souls if you work together. You will not control it but nothing to stop it making an agreement with its creator.