Does the Tentacle of the Deeps get bonus damage from Spirit Shroud?

Does the Fathomless’ Tentacle deal extra damage from the Spirit Shroud spell as it is you doing the attack via the tentacle? If so does the target have to be within 10 feet of both the warlock and the tentacle?

Tentacle of the Deeps: As a bonus action, you create a 10-foot-long tentacle at a point you can see within 60 feet of you. When you create the tentacle, you can make a melee spell attack against one creature within 10 feet of it. On a hit, the target takes ld8 cold damage, and its speed is reduced by 10 feet until the start of your next turn. — Tashas p.72

Spirit Shroud: Until the spell ends, any attack you make deals ld8 extra damage when you hit a creature within 10 feet of you. — Tashas p.108

Can Tentacle of the Deeps be cast on the surface of water?

The Warlock subclass The Fathomless has an ability called Tentacle of the Deeps that reads:

You can magically summon a spectral tentacle that strikes at your foes. As a bonus action, you create a 10-foot-long tentacle at a point you can see within 60 feet of you. The tentacle lasts for 1 minute or until you use this feature to create another tentacle. When you create the tentacle, you can make a melee spell attack against one creature within 10 feet of it. On a hit, the target takes 1d8 cold damage, and its speed is reduced by 10 feet until the start of your next turn. When you reach 10th level in this class, the damage increases to 2d8. As a bonus action on your turn, you can move the tentacle up to 30 feet and repeat the attack. You can summon the tentacle a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

Would that be able to stand on the surface of water?

Can the Fathomless’ tentacle be attacked?

I started playing a Lurker in the Deep Warlock, and have now updated it to a Fathomless Warlock due to the recent update. We came up to a situation where the tentacle was the only thing in attack range of someone, and our DM decided to have them attack the tentacle, at which point they asked me how that works. As far as I can tell there’s nothing describing what happens when it’s attacked/if it can be attacked. I assume a lot of this is up to the DM, but a lot of how the tentacle works is very vague in terms of it occupying physical space.

Can a Fathomless Warlock move their Tentacle of the Deeps without attacking?

In Tasha’s Cauldron of Everything, a warlock with the Fathomless patron can summon a Tentacle of the Deeps, whose description includes the line

As a bonus action on your turn, you can move the tentacle up to 30 feet and repeat the attack.

"Can…and" seems to suggest that you must do both: move and attack. "Up to 30 feet" means you could move it 0 feet and repeat the attack, but can you move the tentacle without attacking?

What is the weapon attack damage of a tentacle rod?

The tentacle rod’s description includes the following (emphasis added):

Made by the drow, this rod is a magic weapon that ends in three rubbery tentacles. While holding the rod, you can use an action to direct each tentacle to attack a creature you can see within 15 feet of you. Each tentacle makes a melee attack roll with a +9 bonus. On a hit, the tentacle deals 1d6 bludgeoning damage.

Answering this recent question, I concluded that the three attack feature of the tentacle rod is incompatible with extra attacks. In this older question, it was concluded that it is also incompatible with opportunity attacks.

However, I was then wondering, how making a normal weapon attack would work with the tentacle rod (without the three attacks property). This is clearly possible and in the case of the opportunity attack it can very well be worthwhile if you do not have better plans for your reaction. Usually, magic weapons have the respective item category (e.g. the scimitar of speed, which says "weapon (scimitar)") which defines a weapon damage in that those weapon types are detailed in the PHB (p. 149).

The description clearly states that the rod is a weapon (vide infra), its category, however, is rod. The magic item categories (DMG pp. 139-140) state that a magic staff can be used as a quarterstaff unless stated otherwise, while a rod is "A scepter or just a heavy cylinder". This was confirmed in this question about rod of the pact keeper.

It seems therefore, that the tentacle rod is a weapon by RAW but has no weapon type or weapon damage defined.

The rules on improvised weapons (PHB pp. 147-148) state:

An improvised weapon includes any weapon you can wield in one or two hands, such as broken glass , a table leg, a wagon wheel, or a dead goblin. Often an improvised is similar to an actual weapon an can be treated as such. For example, a table leg is akin to a club.

It further states:

An object that bears no resemblence to a weapon deals 1d4 damage (the DM assigns a damage type appropriate to the object).

Now the last part should not apply because the rod clearly is a weapon. I can simply decide what weapon the rod is like (probably a quarterstaff, club, or a whip). I am wondering, however:

Is there anything more clear on the subject, either additional rules on improvised weapons, or specific information on the tentacle rod, that would give guidance on the matter?

Can a Tentacle Rod be used with Extra Attack?

In a recent game our Monk used a Tentacle Rod to attack three times (per its normal use), then used his Extra Attack to attack three more times, then used his Bonus Action to deliver an unarmed strike. For a total of 7 attacks every turn.

Is this, as I believe, an incorrect reading of the rules?

My reasoning for attacks 4-6 are that the Tentacle Rod states (it’s long because I’m trying to be thorough):

While holding the rod, you can use an action to direct each tentacle to attack a creature you can see within 15 feet of you.

(Emphasis mine.) It doesn’t say Attack action, it says an action, and I would say that, since it specify an Attack action, and the Rod is a magic item that isn’t a weapon, that the action would be "use an object"

By the same token, the Monk rules state:

When you use the Attack action with an unarmed strike or a monk weapon on your turn, you can make one unarmed strike as a bonus action

If the action isn’t an Attack action, then the Bonus Action cannot be used for an unarmed strike.

This would mean that the Monk can get either 3 attacks with the Rod, or take his standard Attack, Extra Attack, and unarmed strike, which is still 3 attacks.

This is how I read the rules. Also, getting 7 attacks at 5th level seems to break action economy, but that’s more of a "sniff test" that a rule I can actually point to.

I found this question from a year and half ago asking basically the same thing, but about Multiattack. However, Multiattack and Extra Attack aren’t exactly equivalent, neither are PC actions and monster actions, so I’m inclined to think it doesn’t apply.

Thank you.

P.S. I’ve seen this player make similar mistakes to his detriment, so I’m pretty sure any mistakes here are 100% accidental.

Does activating a Tentacle Rod break the invisibility spell?

The Invisibility spell ends when the target attacks or casts a spell:

The spell ends for a target that attacks or casts a spell.

The "Tentacle Rod" magical items lets the user direct three tentacles to attack target(s):

While holding the rod, you can use an action to direct each tentacle to attack a creature you can see within 15 feet of you. Each tentacle makes a melee attack roll with a +9 bonus. On a hit, the tentacle deals 1d6 bludgeoning damage. If you hit a target with all three tentacles, it must make a DC 15 Constitution saving throw. On a failure, the creature’s speed is halved, it has disadvantage on Dexterity saving throws, and it can’t use reactions for 1 minute.

Does activating the Tentacle Rod break the invisibility spell? I’m not sure if "directing each tentacle to attack" counts as attacking yourself.

Can you use a Tentacle Rod to make Opportunity Attacks?

In our game we have recently found a Tentacle Rod/Rod of Tentacles found in the DMG.

The weapon states

While holding the rod, you can use an action to direct each tentacle to attack a creature you can see within 15 feet of you.

Because it requires the PC to use an action to direct the weapon to make an attack does that mean you would not be able to make Opportunity Attacks as they require a Reaction not an Action?