Windthief activation.

[Arkiham]

So, it doesnt say at what point you can activate this, 

So I can activate it when ever i want and (according to the rules)  move up to double their movement characteristic and fly whilst doing so.

 

So. Can I put it on a unit, wait for my opponent to charge me, let them finish shooting and activate it then, and move double my movement where ever I want.

Or wait till My opponents movement phase, wait for them to finish, and move just before they charge me. Baiting them into a advantageous position for me to counter charge? 

[Mayple]

What is windthief, which unit is using it? A reference is generally helpful, as we don't neccesarily know what you're referring to based on the name of an ability/spell

[AverageBoss]

6 hours ago, Mayple said:

What is windthief, which unit is using it? A reference is generally helpful, as we don't neccesarily know what you're referring to based on the name of an ability/spell

Windthief Charm is an artifact available for Disciples of Tzeentch. And it can't be used on units (don't know if that's just poor wording on TCs part), only on heroes.

To the TC, as the item does not have any frame of when it activates (it does not specify a phase, nor does it even specify a specific players turn), RAW it can be used at ANY time.

[Arkiham]

[Mayple]

That is either terrible, terrible wording, or just as intended. 

As written, I see no reason why you couldn't use it at any time. 

 

A counter argument would be defining movement, and concluding that movement out of turn is no movement, so you could only do it during your own movement. I wouldn't make that argument though. It seems pretty clear to interpret it as 'whenever', at least until GW says otherwise, or house-rules deny you.