This page includes major spoilers from Star Wars Rebels Season Three, so just like in my previous article, if you don't want spoilers, leave the page! If you don't care about spoilers, I'll go ahead.
It was confirmed that the possible ending of Rebels will be the two-part season finale "Zero Hour", in which Grand Admiral Thrawn discovers the location of the rebel base. In "Warhead", an Imperial droid named EXD-9 infiltrated the base on Atollon. RA-7 protocol droid AP-5, former Lasat guardsman Zeb Orrelios, and obsolete C1 astromech droid C1-10P, or "Chopper", fought it and shut it down.
Shortly after AP-5 shut EXD-9 down, he discovered a proton warhead inside EXD-9 that was counting down. Before it detonated, Chopper froze the countdown circuit to give them time to think. A message from "Fulcrum", or Imperial Agent Kallus, said that if EXD-9 remained out of contact, the Empire would come after it, and soon.
Zeb told AP-5 to allow EXD-9 to return to the Empire, but the warhead would explode before the Imperials could upload its data of Atollon and take some more of the Infiltrator droids with it. Their plan went perfectly. The warhead inside EXD-9 exploded, taking an entire Star Destroyer with it. Both Kallus and Thrawn noticed.
Kallus and Thrawn met later. Thrawn told Kallus that what Zeb, AP-5, and Chopper did had narrowed his search to 94 planets, including Atollon, all of which were surveyed by EXD-9 and his comrades.
That's all for now. See you next time on anthonythomas.wikia.com!