What Verdugo describes isn’t exactly correct. When the Dragon’s Claw kingdom was released, it was mid-week and the current event was actually Maugrim Woods. At that time, I opened a bunch of glory, gem and gold chests trying to pick up all the new common through epic troops, and hoping that I might pick up a TDS by luck (I didn’t). The following week, they released the last two Dragon’s Claw troops (Dragonian Rogue and Couatl) and made that the Kingdom Event. At that point, I started using event chests and picked up my Dragon Soul.
You can always check the “news” tab on the main game screen and it should tell you what the current event is.
I would expect that they will probably have a two-step release for Blackhawk: Step 1 will be opening up the Kingdom itself and dropping most of the troops into the appropriate chests. At that point, Kraken will be available in Glory and Gem chests, but will be one of 30 or 40 legendaries, so odds will be slim of picking him up. Step 2 will be a kingdom event where they release Bonnie Rose and Mimic, at which point Kraken will be available in event chests so you can target him exclusively (while also picking up a ridiculous number of Sharkeys).