Nathor Solo began teaching Moses the ways of the Force in 1361 ABY. In 1362 ABY, Moses used the Force to tame a yearling sickle tailed lion whom he named Kamau. Two years later Moses returned to Dathomir to buy a horse and bought a black gelding with a white stripe on his forehead. He named his gelding Kol after his ancestor Kol Skywalker. He bonded quickly with Kol, who seemed to enjoy being ridden by Moses. Nathor was not surprised that Moses was stronger in the Force than he was, but soon learned that Moses was less than twice as powerful as Obi Wan Kenobi and that his cousin Marina Skywalker was twelve times more powerful than he was. However, Nathor and Jenify also realized that although Moses was weaker in the Force than his cousin, he surpassed every Jedi apprentice in the Galaxy in dueling skills.
In 1363 ABY, Moses constructed a blue bladed lightsaber while his cousin Marina constructed a green bladed one.
In 1365 ABY, two days after Moses's twentieth birthday and four months after Marina's twentieth birthday, Nathor and his wife gave the two cousins their final trial: track down and confront the One Sith Emperor's Wrath Darth Viper. Moses and Marina were told to fight Viper together, as Moses was not powerful enough to defeat the Wrath alone and Marina was not skilled enough with a lightsaber to fight Viper alone.
Marina meditated on the Force to find Darth Viper's location but had no success. She decided to convince some Triumvirate in exile spies to find Viper's location.
Four days later, a Sith army assaulted an army of Jedi and Triumvirate loyalist soldiers on Yavin 4. Darth Viper was spotted leading the attack. This news quickly reached the Skywalker cousins, who jumped into hyperspace and arrived on Yavin 4. Over half of the Sith on Yavin 4 had been killed by the time the Skywalkers arrived. However, a Chiss fleet led by non Sith Admiral Froin arrived two hours after the Skywalkers arrived and the tide began to turn in the One Sith's favor once the Chiss troopers exited their ships. Moses and Marina decided to attack them from the rear. Marina sneaked up behind the Sith army and used a powerful Force push on the Chiss and Sith from startled the Sith. Darth Viper turned out to be one of the Sith affected by the Force push and had just gotten back on his feet when Moses charged at him. Viper realized Moses was a descendant of Cade Skywalker and ordered the Chiss and other Sith to hold their fire. She yelled, "Hold your fire! I will deal with these Skywalker scum myself." She looked at the closest Sith Lord to her, who was a Lethan Twi'lek, and said, "Lord Liza, you take command of the army until I have killed both Skywalkers."
Moses's sickle tailed lion companion Kamau leaped at Viper. However, the Emperor's Wrath used Force Lightning on Kamau, who was killed in ten seconds.
Moses Skywalker then flew into rage and began turning to the dark side. He brandished his lightsaber wildly. Viper tried to rely on fear and hatred to help her against Moses, but Moses was too skilled with a lightsaber even for Darth Viper and had even more rage than her so he easily sliced off her right arm. Marina then used Force Push on the Wrath to prevent her from grabbing her lightsaber with her remaining hand.
Moses leaped at Viper, who unleashed Force Lightning at him. However, Moses easily blocked the lightning with his lightsaber and sent the lightning back at his opponent. The lightning began to wrinkle her skin very badly.
Fearing for the Wrath's life, a Zabrak Sith charged at Moses, but Marina used Force Levitate on him and hurled him into the Jedi frontlines.
Darth Viper realized that if she continued to use Force Lightning at that moment, she would die. So she retracted the lightning and said, "Go ahead, Skywalker! Finish me off! If you do, you will be serving my Master while I go to the Netherworld of the Force!"
Marina shouted, "No Brother! Don't do it! You don't want to serve the Emperor and become my enemy and the killer of everyone you love, do you? Remember what happened to our ancestor Anakin Skywalker and what almost became of Luke when he defeated his father? Besides, killing Viper won't bring Kamau back."
Moses then looked in horror at what he had almost done. He then cut off Viper's legs and said, "You're right my sister. Let's just leave Viper to her master's mercy and return to the Jedi Council. Viper will be much weaker in the Force now that she has one arm and no legs. Emperor Pharos will decide her fate now."
So Moses and Marina ran to their ship and flew back to Ossus to report how they dealt with Darth Viper.