The Ultimate Combination!! Black Zarak, the New Lifeform

With the location of the Decepticon base now known by the Autobots, they have all met together on an island nearby to the base and are discussing their battle plan. Whilst the Autobot Pretenders are left behind for reasons that are never made clear in the episode, the rest of the Autobots take off and head to the Decepticon base.
 

At the Decepticon base, Black Zarak has arrived and Devil Z tells Giga and Mega that he has been called here to help them fight the Autobots as now that they know the location of the base, they will surely stage an attack soon. Giga suggests they head off and fight them before they get hear but Devil Z says that he has the "key to victory" and that the Autobots will be destroyed when they arrive.
 

The Autobots get to the place and as they get closer to the main structure, they are detected by radar and a load of Seacons arrive to attack them. Knowing that if the base submerges before they can attack it will make the battle a lot more difficult, Ginrai heads in towards it whilst all of the other Autobots attack the Seacons.
 

Before he can get inside though, the Decepticon Pretenders and Godmasters are waiting for him at the top of the base and start their attack as the other Autobots continue to fight the many Seacons, but even though they are destroying loads of them, more keep appearing, and then to make things worse, Turtlar appears and transforms with some of the others into King Poseidon.
 

He is soon destroyed by Maximus' firepower though and as Super Ginrai transforms into God Ginrai the other Autobots help him to fight the Decepticons, and with no signs of Black Zarak anywhere they are outnumbered and outgunned. Devil Z is watching the battle and after calling his minions all worthless, he tells them to retreat as the base starts to go under the water.
 

God Ginrai takes a group of Autobots with him and tells Grand and the others to wait above the sea for now, and has his group enters the water they find a glass tube used in retracting the base. Ginrai destroys this and they are all sucked inside and when they stop they find themselves in the base's main hangar. But Devil Z has learnt of this and says that he will now show, for the first and only time, his true form.
 

Whatever this new form is, in involves lots of flashing lights and a quick glimpse of what seems to be a space foetus and then Devil Z moves towards Black Zarak and merges with him.
 

As Devil Z begins to rise, the Autobots think that he is trying to run away and he is, but before departing he bodes them all farewell and then uses his power to crumble the floor they are standing on, causing them to fall down. When they get up, Devil Z is gone and they see that now he has merged with Black Zarak, he has extreme amounts of power and if they don't stop him it could mean the end for the Earth.
 

Ranger then spots some water and reckons that it must be part of an underwater volcano and if they head up, it should hopefully take them to an exit. As God Ginrai takes Shūta and Cab up first, Devil Z tells the remaining Decepticons that he has planted a bomb in the base's armoury and when it explodes, it will destroy the entire base and the Autobots with it. Overlord at first says he can't do that as Wilder and Bullhorn are still down there but as the Decepticon leader doesn't care about them, he is forced to obey and go with this new plan and they all leave the base.
 

As Ginrai gets to the top he tells Shūta and Cab to go to Grand Maximus and bring back the rocket packs as he wants to use them, but as they set off to do this they hear the Decepticon Pretenders talking and find out about the bomb which is going to explode in 20 minutes time. They head back the way they came and find that Ginrai has bought Ranger and Road King up with him, and they tell him about what the Decepticons plan to do now. Ginrai heads back down and contacts Clouder, who heads out of Grand Maximus brining the rocket packs with him.
 

As Ginrai reaches the bottom, he finds Lightfoot and finds out that Wilder and Bullhorn are also down here, and he tries to tell them that they will die if they don't get out of here but neither of them believe him saying that their Decepticon friends would never do something like that to them. Meanwhile Clouder reaches Shūta's group and is told to go down and give the rocket packs to Ginrai.
 

As Clouder arrives, Ginrai tells him to take Lightfoot back up to the surface and then for the Autobots to get to Grand and for them all to retreat whilst he tries to convince Wilder and Bullhorn that the Decepticons have left them here. As the other Autobots escape, the bomb goes off and soon the entire base begins to blow up.
 

Ginrai saves the two of them just in time as the base is completely destroyed, and everyone is happy to see that he's made it out in one piece. As they fly away from the ruined Decepticon HQ, the narrator takes over by saying that whilst the base is gone, what could the Decepticons possibly plan to do next?

What Devil Z actually is is never explained in the series, and what the space foetus could mean is anyone's guess. See the FAQ for a bit more on the limited information available on him.