Emperor Palpatine (AKA, Darth Sidious, AKA, The Omnipotent Battle Leader) is the most powerful and influential Dark Lord of the Sith in galactic history. Once a Senator of Naboo and then Supreme Chancellor of the Old Republic, he secretly manipulated both sides during the Clone Wars to weaken the Jedi Order. Finally, he eradicated them, through Order 66 (With very few survivors). He re-formed the Republic into the Galactic Empire and became its self-proclaimed Emperor, with intentions of ruling the galaxy forever.
In 4 ABY, he was killed by Darth Vader, now redeemed as Anakin Skywalker once more. His Empire fractured after his death and, without a permanent leader, went into several conflicts with the fledgling New Republic and with themselves. His spirit was alive, thanks to an ancient Sith technique, and transfered to a clone body on Byss. With Palpatine reborn, the IR's might returned, along with a huge array of superweapons like the Eclipse-class SSD, the Sovereign-class SSD, the World Devastators and the Galaxy Gun.
The IR became the Galactic Empire (Or, in this case, the Dark Empire) and the New Republic became the Rebel Alliance once again. He commands the Eclipse-class SSD, when in space, and as himself, when on the ground. He's only available at era 3 (His era) and is the leader of the IR. His appearance, along with the Sovereign-class SSD, makes the IR, of era 3, the most dangerous and most powerful faction.
Born into a rich family, Palpatine was taught the way of the Dark Side by Darth Plagueis. He soon became Darth Sidious and trained a Sith assassin named Darth Maul. Sometime after the Battle of Naboo, Palpatine became Supreme Chancellor of the Old Republic and, later, murdered his master while he was sleeping.
After the death of Darth Maul, he trained Count Dooku, known as Darth Tyranus, and created the CIS to combat the Galactic Republic. He also secretly aided the creation of the Clone Army. When the Clone Wars broke out, he carefully manipulated both sides to weaken the Republic and the Jedi Order. He was then captured by General Grievous of the CIS army and was rescued by two Jedi, who infiltrated the General's ship.
His apprentice, Count Dooku, was slain by Anakin Skywalker, who would shortly become Darth Vader. Thanks to Anakin, Mace Windu and three other Jedi Masters came to the Chancellor's office to arrest the Sith Lord. Darth Sidious easily killed all 3 Masters and battled with an experienced Windu. When Skywalker arrived, he was at the jedi master's mercy. The dark lord tried to lure Anakin to the Dark Side. He succeeded and Anakin cut off Windu's hand, allowing Sidious to kill him.
Anakin was then knighted as 'Darth Vader' and sent to kill the Jedi at the Jedi Temple. Afterwards, he went to the CIS council at Mustafar and murdered them all. Meanwhile, Palpatine issued Order 66 to make the clones kill their jedi commanders. When Vader was defeated by jedi master Obi-Wan Kenobi, he rescued Vader and rebuilt him with an armored suit.
He formed the Galactic Empire, from the ashes of the Old Republic, and installed himself as Emperor. He ruled the galaxy for over 20 years before he met his demise at Endor. Just as he was about to kill Luke Skywalker, Vader turned on him to save his son and threw the Dark Lord into the Second Death Star's reactor core. Anakin, redeemed, died soon after he revealed his face to his son.
After his first death, the Empire fractured into many sectors. Various warlords like Zsinj, Treuten Teradoc and Grand Moff Ardus Kaine carved out their own kingdoms during the chaos that followed. Their territory was slowly absorbed into the, fledgling, New Republic with the liberation of Coruscant and the death of important leaders like Sate Prestage, Ysanne Isard and Grand Admiral Thrawn.
Palpatine's spirit, however, survived Endor and returned in a clone body inside a secret facility on Byss. Along with his return were brand new superweapons like the Eclipse-class SSD, the Sovereign-class SSD, the World Devastators and the Galaxy gun. The remnants of the Empire joined him and he commenced Operation Shadow Hand, taking back many systems through fear and terror.
He was killed a second time during battle of Pinnacle Base after being defeated by the Skywalker twins. He was finally killed during the Battle of Onderon. His personal flagship, Eclipse II, was hijacked by R2-D2 and collided with the Galaxy Gun. One shell was fired at Palpatine's capital, Byss, killing billions of Imperial personel and destroying most of his massive fleet. The Empire is weakened even more and lost most of its newly conquered territory. The warlords ended up fighting each other once again.
Palpatine is the IR leader, during era 3. Therefore, he can reduce the price for everything on a planet he is stationed at. He commands the SSD Eclipse, which has an axial superlaser, that can destroy most ships in one shot, and gravity well generators, to stop retreating units.
His ship is much weaker than an Executor-class SSD in terms of armor, shields and weapons so be careful when engaging opposing forces that have SSD's themselves (Like Wedge's Lusankya or Ardus Kaine's Reaper). If you encounter these ships, just either zap them with your superlaser (If you decided to save the laser for them) or just jump to hyperspace (Since the Eclipse has no engine hardpoints).
He fights on the ground as himself. He has lots of health and has two powerful force abilities.
In space, use the superlaser to destroy anything in 1 shot (Excluding Excecutor-class SSD's). Retreat, if you think his ship is about to be threatened. His gravity well generators can stop an enemy force from escaping so you can destroy them without the help of the expensive and fragile Immobilizer 418 or the expensive and undergunned Interdictor. Be careful going into land combat with Palpatine because, if he is killed, you will lose the ability to construct Sovereign-Class SSD's and Praetor Mark II's (Along with all your powerful era 3 heroes). You'll also lose his Eclipse-class SSD as well.
As the NR and EotH, make a Zerg rush NEXT to Byss after Isard dies. Position your most powerful offensive fleet there and build up defensive fleets. When Thrawn is killed by the AI, move your fleet to Byss immediately and kill all the IR space heroes there. You will suffer heavy casualties but it's worth it.
Get a strong ground force ready and invade Byss. Once on the ground, kill Palpatine and destroy all of his ground forces! By doing this, you have forced the IR to skip era 3 before they were able to build anything. As the PA, you will be unfortunate as you are too far away from Byss and won't be able to reach it, as of era 3.
You will have to advance slowly towards Byss while fighting past Palpatine's massive fleet. Do not bring Kaine or Jerec along, when facing Sovereign or Eclipse-class SSD's, as they can zap your heroes in 1 shot. Instead, bring a large fleet of carriers.
Carriers are cheap and have a massive amount of fighter and bomber squadrons. Use them to destroy the Sovereign and Eclipse-class SSD's. If you're lucky, you'll face him on the ground, where it is much easier to kill him. Also, bring along a few Immobilizer's to stop him from escaping during space battles.