To unlock Master Piccolo, Krillin and Vegeta in Dragonball Xenoverse, you need to meet certain requirements. As early as Level 5 you will encounter your first master. Like everyone else, these three mentors have four skills.
To unlock Piccolo, you have to complete the main quest and achieve Level 5. Once you defeat him in the first fight, he will reward you with the ability "Evil Explosion". With this power you have so often fight until a blue question mark over master Piccolo, gives you to understand that you can compete against him the next fight. Utilize "Evil Explosion" as a finisher and you get "Super Explosive Wave". Now you go the same way as before.
The next time you fight you face with three piccolos. Concentrate your attacks on the turban and the cloak and beat him to obtain the ability to "Light Grenade". In the following three fights you use the skills you learned repeatedly and Master Piccolo challenges you one last time. Defeat him with the "Light Grenade" and he turns his ultimate "Special Beam Cannon" free.
To get Master Krillin in Dragon Ball Xenoverse as a mentor, you must achieve Level 5 and complete part of the Saiyan saga. Defeat him the first time, you will learn the "Orin Combo". Next, you need the friendship bars fill and bring Master Krillin on your parallel quest . He trusts you, he calls you again out and reward you for your victory with the ability "Destructo-Disc".
Ask Krillin about an "Energy Capsule S", then ask him for this in the item shop or farm in a parallel-Quest. Then you can re-fight with Krillin and learned after the Move "Spread Shot Retreat". For the ultimate capability you need a little more work on your friendship, until you can present the mentor again. To give you the move "Scatter Kamehameha".
To counter Master Vegeta, you have to have reached Level 8 and have completed the entire Saiyan saga. Travel to Toki Toki, where you can fight against Vegeta to get after your victory "Galick Gun". Then cultivates your friendship in a conventional manner and includes parallel Quest Nr. 5 from repeatedly until you farm a "Z-soul". After the second battle you get his ability "Final Flash".
The third fight against Vegeta is not so easy, but there are peculiarities not observed. So it is with the fourth and final fight against the champion. Use your learned skills and gain first "Shine Shot" and at the end the ultimate move "Final Flash".