Claw of Acamar

[DonElektro]

In Unearthed Arcana: Warlock & Wizard there is an Eldritch Invocation called Claw of Acamar with prerequisite: The Great Old One patron and Pact of the Blade feature. The description says:
You can create a black, lead flail using your Pact of the Blade feature. The flail’s head is sculpted to resemble a pair of grasping tentacles. The weapon has the reach property. When you hit a creature with it, you can expend a spell slot to deal an additional 2d8 necrotic damage to the target per spell level, and you can reduce the creature’s speed to 0 feet until the end of your next turn.
My questions:
1) The weapon must be a Flail as described in PHB 149 or can be an improvised Flail probably with a higher damage dice and the heavy/two-handed property (considering the flexibility of the Pact of the Blade feature and of course the DM's approval)?
2) As read from the description, the ability to reduce the target's speed to 0 feet activates only when you use spell slots or it's a passive ability who can use just if you hit the target without the expend of a spell slot?

[blurneko]

1) It is a flail as described in the PHB with an added 'Reach' property
2) Only when you expend a spell slot.

[RSP]

In Unearthed Arcana: Warlock & Wizard there is an Eldritch Invocation called Claw of Acamar with prerequisite: The Great Old One patron and Pact of the Blade feature. The description says:
You can create a black, lead flail using your Pact of the Blade feature. The flail’s head is sculpted to resemble a pair of grasping tentacles. The weapon has the reach property. When you hit a creature with it, you can expend a spell slot to deal an additional 2d8 necrotic damage to the target per spell level, and you can reduce the creature’s speed to 0 feet until the end of your next turn.
My questions:
1) The weapon must be a Flail as described in PHB 149 or can be an improvised Flail probably with a higher damage dice and the heavy/two-handed property (considering the flexibility of the Pact of the Blade feature and of course the DM's approval)?
2) As read from the description, the ability to reduce the target's speed to 0 feet activates only when you use spell slots or it's a passive ability who can use just if you hit the target without the expend of a spell slot?

2) Though the passage does read as an alway on 'passive ability,' the majority (at least as I've seen it here) believe the intention is to only have it activate when using a spell slot.

[gabrion]

2) Though the passage does read as an alway on 'passive ability,' the majority (at least as I've seen it here) believe the intention is to only have it activate when using a spell slot.

1) To me, this is a more general question about pact of the blade than Claw of Acamar. However you answer it, it will probably be the same for pact weapons in general. If you get a DM who lets you use pact of the blade to make weapons with different characteristics than the base version, you will likely get the option to do so with Claw of Acamar as well. Strictly speaking though, Pact of the Blade says points you to another part of the PHB for weapon options and gives no indication that characteristics of your pact weapon can deviate from those.
2) The way it's currently written, it works on any attack, without the need to expend a spell slot. This is UA though meant for testing and I would be pretty surprised if this was the intent and they don't fix the comma if/when it goes official.

[MrStabby]

As written, it is always on.

As it is UA use it as a guide rather than RAW and do what is appropriate. I am on the fence about what I would allow, but it isn't too egregious to make it always on as long as the warlock cannot multiclass.