The dreadclaw drop pod in Betrayal features as a unique unit available to only the Sons of Horus. Book 3 (Extermination) provides the Anvillus pattern dreadclaw to other legions, but in Betrayal, there is only the one legion that can use them!
So, what is this unit about? Well, its a drop pod that can also take off again. Hence, rather than being immobile all game and making a terrain feature, the dreadclaw is both a flyer and a hoverer. That said, it does not come with any armaments, apart from the frag assault launchers and instead must deep strike (and be held in reserve along with any on board unit from the start of the game).
The uses for the dreadclaw are probably going to be limited to delivering the cargo (which I suspect would be an assault orientated dreadnought or contemptor, despite being able to also take seekers, justaerin terminators, command squads, and veteran squads). The combination of being an assault vehicle plus having the frag launchers makes it exceptionally good for this! Deep strike the melee dreadnought and then take off for elsewhere; pick up anything that requires to be elsewhere.
To be honest, I'm not sure its worth the points cost over a regular drop pod, at least in the form displayed in Betrayal. I do like the combination of the frag launchers and it being an assault vehicle, but the price is the lack of drop pod assault and inertial dampeners. But equally, no other legion has it in Betrayal, so could be used for uniqueness in the Sons of Horus.