You follow the Way of the Rising Sun, a group of monks that practice the tutelage of the great Sun. They are known for being juggernauts on the battlefield with mastery and control over their own body, healing wounds like nothing and vaporizing their enemies with a single blow. The most tenacious battlefield legend about them tells of how no matter how hard you hit a monk of the Rising Sun, they'll only get back up stronger.

By choosing this subclass, you'll be a tankier monk with a subtle focus on fiends and undead. For good synergy with this class' features, try to keep your Constitution high. The Tough feat also works quite well.

Path of the Sun's Guidance

At 3rd level, you have begun to reap the benefits of following the path of the Rising Sun. You draw on the sun's light for your strengths, using a deviation of Ki. Whenever you make an attack with an unarmed strike or a monk weapon, you may spend a number of Ki points up to your level. If you do, add that many d8s of radiant damage to the attack. You may pay these ki points before or after you know the attack has hit.

Additionally, you do not tire easily, being imbued with energy from the sun's rays. You gain Exhaustion at half the rate others do. You gaining one level of Exhaustion is the equivalent of others gaining two. You also may tap into the Sun's light, imbuing objects with it for a short time. You gain the Light cantrip.

Endurance of the Light

At 6th level, the hardy tenacity of sunlight flows through your veins, turning you into a juggernaut. Whenever you lose 20% of your maximum health, you gain ki points equal to that amount of health/4. So for instance, if you have 100 health and drop to 80, you would gain 20/4 ki points, or 5. If you have 150 health and drop down to 120, you would gain 30/4 ki points, or 7 (rounded down). This ki cannot make you exceed your maximum. You also do not need to lose the health in one attack; it can be many rounds or attacks  as well.

Additionally, all radiant damage you deal ignores resistances, and treats immunity as resistance. You may also treat a 19 or a 20 on the d20 as a critical hit, if you are attacking an undead.

Champion of Light

Beginning at 11th level, your mastery over the ways of sunlight and radiant justice has given you many ways to utilize your ki. You may spend ki points in the following ways:
- As a bonus action, you may use 2 ki points to increase your AC by 1 for one minute. You can activate this up to three times in one bonus action. You can only increase your AC in this manner up to three times at once.
- As a bonus action, you may use 2 ki to add 1d10 radiant damage to your unarmed and monk weapon attacks for one minute. You may only have one instance of this benefit active at once.
- As a bonus action, you may use 4 ki to gain temporary HP equal to your monk level plus your Wisdom modifier.

Paragon of the Sun

At 17th level, you become the pinnacle of the Sun's power, infusing your veins with its power. This may show in physical changes, perhaps along the lines of changing your hair to a golden hue, giving your eyes a radiant glow, glowing in the dark, and your veins under your skin shining with light. Or any other attribute you may desire.

Mechanically, you gain resistance to radiant damage. As an action and once per long rest, you may gain the following benefits for one minute:

- At the beginning of your turn, you regain HP equal to 5 + your Constitution modifier.

- Once per turn, you may add radiant damage equal to your character level to one damage roll.

- If you hit a fiend or undead, (Or any other creature with aversion to sunlight, at the DM's discretion) and reduce them to less than half of their max HP, they must make a Constitution saving throw (DC = 8 + your proficiency bonus + your Wisdom modifier). If they fail, they instantly vaporize.