Hearts of Darkness (The War Master).

Audio  Spoilers ahead, warning, spoilers ahead.  If you've not listened to Hearts of Darkness, stop reading here.  That caution proffered, the fact I'm reviewing all four episodes should be a strong indication that this is a bit more than the cover suggests except to say, within this pre-amble, that what we have here is essentially a bonus Eighth Doctor Time War box set under a different guise and so therefore essential to anyone at all interested in this incarnation (assuming printing McGann's face on the box wasn't enough already).  

The Edge of Redemption

Not having really followed The War Master series unless McGann's face is printed on the box, the changes to the renegade Time Lord's personality seemed to be a character choice made by the writers in order to sustain him as a protagonist over many episodes.  Even the lightened shades of Jacobi's performance seemed to be a choice to indicate that they're working towards Professor Yana or some ethical re-engineering in a boxed set I'd missed.  He's very specifically not attempting a McGann impression but rather what a Jacobi incarnation of the Doctor might be like.

The Scaramancer

Why doesn't the Doctor reveal his identity earlier, especially when The Scaramancer obviously has cause to have the body he's currently inhabiting?  The more obvious answer is to delay the end of the episode surprise but the in-story explanation could be that he sees the Master's identity as a way of opening doors and taking steps that he'd find morally dubious in his own skin.  My tired old brain did later wonder why the Doctor didn't recognise her from their old Doom Coalition days, until I remember that it's a different character.  She was the The Sonomancer, completely different 'mancer.

The Castle of Kurnos 5

Finally the big reveal that the Master is essentially a supporting player in his own series and that the character we've been listening to for the past couple of hours is the Eighth Doctor with a different face, the no guns rules now making perfect sense.  The Castle of Kurnos 5 offers us some prime Eighth Doctor shenanigans in the flashback with a witty one-off companion, a host of fantasy tropes and walking straight into a trap.  I know it's his job, but I'm always impressed with how McGann modulates his performance to reflect were the Eighth Doctor is on his timeline, at least in terms of the audios.

Cognition Shift

Which makes his portrayal of the Master even more sinister, especially when he says "the line".  Like Jacobi, he's proposing what his incarnation of the Master might be like, which is to say just as charming and in such a way that you can believe that he'd become a Kurtzian figure leading a population of dupes.  It's unfortunate his plan isn't allowed to succeed before its foiled.  Having the Master's consciousness consume the entire Dalek fleet is an epic, horrific prospect along the lines of the entirety of humanity having John Simms's face and on television would surely be the stuff of an RTD cliffhanger, the Dalek Emperor booming "I am the Master and you will obey me.  Or I will exterminate you ..."

Placement: The Doctor talks about becoming more involved so just before The Time War boxsets.