This spell should be upgraded and need some more info to make it clearer: the plane of force is probably invisible, which gives the sword advantage on all it's attacks (unless opponent has true vision...). Damage should be increased as it's a 7th level spell.

It’s a sword  🗡 you should be able to at least carry it.

4th level Spiritual Weapon is more powerful than this spell, and requires no concentration.

This spell is very week for it's level, especially in comparison to spells like Forcecage, Prismatic Spray and Crown of Stars.

Terrible spell.  Upcast Spiritual Weapon instead, you canny multiclasser....   Nearly every other spell available to every other class is a better use of your concentration.

This is what the sword looks like, it says plane of force because it can't be broken.

You have to hit with it three times just to do more force damage than magic missile cast at seventh level... There is no scenario that would ever make this spell worth a seventh level slot. Bigby's hand is two levels lower, does more damage, and has multiple other uses and crown of stars is the same level, does more damage, and doesn't require concentration.

Force magic isn't concealed by an illusion though, it's transparent. Would a monster with true sight be able to see air? No.

It's worth noted that the sword can deal up to 6d12 force damage on the first turn (with two successful hits: action *and bonus action), and 3d12 force damage on subsequent turns. Which makes it somewhat better than some people think. In our campaign, we also allow the sword to strike creatures on the Ethereal Plane (assuming you can see them). 

All things considered... Spiritual Weapon is better.

If this is gonna try to be a better spiritual weapon, make it BETTER. Maybe it can slash up to 3 adjacent 5 foot squares, it can be wielded as a regular sword that deals 3d10 base damage, make it move the target or knock them prone... SOMETHING

Read it again. Spiritual Weapon scales per TWO levels. It would take a level 8 Spiritual Weapon to match this spell.

Spiritual weapon level 6: 4d8, averaging 18

This Spell level 7: 3d10, averaging 16

Spiritual Weapon level 6: 3d8 damage, level 8: 4d8 damage

Mordenkainen's Sword level 7: 6d10 on the first turn (make an attack as part of the action to cast then bonus action to make the attack again) and 3d10 every turn after

Both spells last a minute, so 10 turns. So level 6 Spiritual weapon averages at 135 after its duration. Mordenkainen's Sword at level 7 averages at 181 damage after its duration. Spiritual weapon at level 8 averages at 180 after its duration... Mordenkainen's Sword averages at more damage than Spiritual Weapon even when Spiritual weapon is cast at one level higher. Spiritual Weapon is also available to Clerics (not including abilities that allow access to extra spell lists) while Mordenkainen's Sword is available to Bards and Wizards so that might also affect the decision of which one to use. This spell is really not as bad as people think. It's not superb but it's not terrible.

Just wondering, can this be used in conjunction with Green-Flame Blade? That spell says that you must make a melee attack with a weapon as part of the casting, is there anything in the rules that says you couldn't use the sword this spell conjures as the aforementioned weapon? That way, you'd make one attack using MS as your bonus action, and then another attack with MS + GFB using your action.

Unfortunately no you can't use MS for the GFB attack. When using MS you create a plane of force that makes melee spell attacks while GBF has you make a melee attack with a weapon. MS isn't a weapon and essentially GBF requires a melee weapon attack, not a melee spell attack. Though it's up to your DM if he wants to interpret the rules or change them in another way. As its worded, it doesn't work.

Quote from TriseAlpha >>

Read it again. Spiritual Weapon scales per TWO levels. It would take a level 8 Spiritual Weapon to match this spell.

 Spiritual Weapon also adds your spell modifier to the damage, so:

2nd 1d8+mod

4th 2d8+mod

6th 3d8+mod

8th 4d8+mod

All without concentration and being cast as a bonus action. 

Ah, you're right, I guess it technically isn't making a weapon. Should've read that more closely, thank you.

Quote from Aragorn1389 >>

Spiritual Weapon level 6: 3d8 damage, level 8: 4d8 damage

Mordenkainen's Sword level 7: 6d10 on the first turn (make an attack as part of the action to cast then bonus action to make the attack again) and 3d10 every turn after

Both spells last a minute, so 10 turns. So level 6 Spiritual weapon averages at 135 after its duration. Mordenkainen's Sword at level 7 averages at 181 damage after its duration. Spiritual weapon at level 8 averages at 180 after its duration... Mordenkainen's Sword averages at more damage than Spiritual Weapon even when Spiritual weapon is cast at one level higher. Spiritual Weapon is also available to Clerics (not including abilities that allow access to extra spell lists) while Mordenkainen's Sword is available to Bards and Wizards so that might also affect the decision of which one to use. This spell is really not as bad as people think. It's not superb but it's not terrible.

 Spiritual weapon gets the spellcasting modifier (probably +5) added to the damage. So over its duration it averages 185 damage if cast at level 6.

All for a lower slot and no need to use concentration.

This is absolutely one of the worst spells I've ever seen. It's a 7th level spell that deals less damage than a 1st level spell cast at 2nd level

This spell does 3d10 damage when cast at 7th level.

Inflict wounds, a 1st level spell already deals 3d10 damage at 1st level so if it's cast at 2nd level, it'll deal more damage than this.

It's cool, but if you want something like this, pick up flaming sphere or spiritual weapon.

Now that Blade of Disaster out in Icewind Dale, this even worse and should not stay lvl7.