Light + Nick + Pact of the Chain (Waiving Light+Nick Additional Attack to let Familiar Attack).

Quote from Tarod_ >>

 Hi friend!

Yeah, sorry, I missed this thread, but I shared the following post yesterday in Battle Familiar and Pact of the Chain (EDIT: StonyMac was there, indeed)

 Hola amigo! Thank you it's okay the thread may have been in relation with another game feature that forgo attack, like Beast Master but all i remember was the funny justification. 

Yeah, that was a witty comment posted by jl8e in one of the linked threads.

Quote from jl8e >>

Quote from AntonSirius >>

I agree that War Magic would work with Haste. I just don't see, within the rules, what the difference is between an extra attack granted by Haste and an extra attack granted by Light/Nick. They're both done as part of an Attack action

 One is conditional on using a Light (possibly one with Nick) weapon to make it. The argument is that, because of the preconditions, you can't go "I'll attack with my scimitar... just kidding, I cast a spell." It has merit, but, as I said above, there's not enough text there to officially rule either way.

So I guess that instead of "kidding, I cast a spell", in this case it would be "kidding, my familiar attacks".

Quote from David42 >>

1) Pact of the Chain: "when you take the Attack action, you can forgo one of your own attacks to allow your familiar to make one attack of its own". 

2) The above does NOT specify that the attack given up must be part of the Attack action - only that the character must take the Attack action and must give up one of their attacks. 

Although I see where you are going with this regarding the wording, I'm not a fan of an interpretation that counts an attack which requires a future Bonus Action expenditure as "one of your own attacks" . . . especially if you can claim to forgo that attack and then immediately use that Bonus Action for something else.  That would defeat the purpose of requiring you to give up some action economy in order to boost the action economy of your familiar.  Although the RAW might allow for such an interpretation, I think that that's clearly not the intent.

I think that a better interpretation is that you start out your turn without any attacks of your own (in general).  Then, after taking the Attack action, you have one or more attacks of your own because taking that action has enabled you to be able to make those attacks.

Quote from Character77006 >>

To use nick don't you need a weapon mastery?   Warlocks do not have that mastery so they to get that somehow.

This is true.  One common way to achieve this is through multiclassing.

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As for the question posed by the OP, in my opinion if you take the Attack action and make your first attack with a Nick weapon (and you have that mastery), then the future / potential Extra Attack of the Light Property becomes "one of your own attacks" at that point.  You can then forgo that attack and provide the action economy to your familiar as per that feature.

Quote from up2ng >>

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Quote from Character77006>>

To use nick don't you need a weapon mastery?   Warlocks do not have that mastery so they to get that somehow.

This is true.  One common way to achieve this is through multiclassing. [...]

 Another option could be with the Weapon Master feat.