The ability to do stuff like a Sayjin! While Sayjins no longer exist on Sol, There are hidden temples in China, Japan and even little pocket dimensions where the knowledge still exists. 

Sayjin Abilities

Choose 2 options at level 3, and one more every 3 levels (6, 9, 12, 15, 18, 20)

Combo Finisher

After using any melee attack (including ki attacks), you can use a ki ability as a final blow. If this hits, regain 1d6 ki points.

Destructo Disk

Spend a ki point to create a disk that does 4D10 damage. You can split this energy to fire 2 disks doing 2d10 damage each. On a natural attack roll of 18, 19 or 20, the target must make a dex save, DC 8+wis+prof. bonus or have a limb severed. 1-left foot, 2-right foot, 3-left leg, 4-right leg, 5 torso, 6-left hand, 7-right hand, 8-left arm, 9-right arm, 10-head 

You may spend an additional Ki point to make the damage HD damage. 

If the target has HD armor, the HP version will not sever a limb.

Fly

You gain a fly speed of 10 x level.

Fusion

To do this, you must be standing next to a willing target who also knows the “dance” and has at least 1 monk level. No other action can be taken. The first fuser must hold their action until the second fuser’s turn. The final product is the higher level character’s level times 1.5, rounded up. The same calculation applies to ki points and proficiency modifier. The higher ability scores of the two are taken. Both players ki abilities are available in the new form. The known proficiencies are shared. A new initiative is rolled.

Ground Slam

Punch or stomp the ground and cause a 10 foot radius of rock juts up around the sayjin. Costs 1 ki point for 1d4 damage/level. Spend another ki point to cause HD of damage. All caught in the area of affect must make a Dex save or be pushed 10 feet away a and be knocked prone. DC 8+Wis+prof mod.

Hyper-Strke

If you take the attack action while unarmed, you may spend a ki point to do another round of attacks. At 7th level, you can spend a second ki point to do this twice in a round, 3 times at Level 14.

Instant Regeneration

As Ana action, spend 1 ki point to heal yourself 1hp/level.

Instant Transmission

As a bonus action, you can spend a ki point to instantly travel 60 feet and 3 ki points to travel to anywhere you’ve been before. You can spend one additional ki point to take someone with you, up to 3 people. A wis save is allowed if they are unwilling. Dc 8+wis+prof.

Kamehame Wave

At the cost of 1 ki point you can harness and channel a blast of your own ki at your enemies while shouting a random bunch of syllables. Damage is 1d8 per level plus wisdom modifier. (Lvl 2 = 2d8+wis)

Ki Spray

Explosions fill a 20 foot circle dealing 1d12 damage per level of the Sayjin. Dex save vs DC is 8+wis mod+prof bonus

Power up!

As a bonus action, and for two key points, you can increase your level buy one for each round spend powering up. Maximum is double your current level. Your movement becomes zero. Doing this takes all of your concentration and you can take no action but the Dodge action. In addition, if you take damage, you must make a constitution saving throw to maintain concentration as a spell caster does. (DC is 10 or 1/2 the damage taken.) Failure means that your concentration is broken and the powering up for this round is lost. You must spend an additional two key points to restart the process. Previous levels gained are not lost. 

Each level gained bestows upon you hit points, AC, actions, attack and damage increases as if you actually had gained those levels.

Primal Influence

You may make a mental connection with a target to inspire primal rage in them. Until the start of your next turn, the target makes its Dex and wis saves at disadvantage and can’t think clearly enough to use special abilities.

Primal Roar

Does not affect Creatures that are deaf or do not have ears. Everyone in hearing range must make a con save or be stunned for one round.

Deflect Attack

As a reaction, you may spend a ki point to deflect an energy attack of HP level. Spend 2 to deflect a HD level energy attack.

Sayjin Defense

At 11th level, you receive a second reaction.

Spirit Bomb

Good aligned sayjins ask permission (evil aligned sayjins take) the power of their surroundings and form a large ball of psychic energy to blast a target. This is done in combination of ki points and hp. The damage done is HD=hp x ki x 10. Dex save for half. DC = 8+WIS+Prof.

Example: 4ki x 50 hp x 10 = 2000HD