In times of the ancient past, the mighty Titans went to war with the gods of old, because the Titans had forgotten kindness and perpetrated injustice. In their combats, there were powerful fighting styles and combat arts perpetrated by both sides, and while the great Titans who first bore these martial arts have long since fallen, their teachings survive to a small and elite cadre of those who are Titanborn. These styles train in utilizing the Ki to transform the physical form in potent ways, using the aberrant magic of the primordial Titans, themselves. These monks find themselves able to grow in size, and even sprout additional limbs as a result. They become truly nightmarish as they become more disciplined in their path, transforming into whirling weapons of doom streaking through their foes. Thankfully for the world at large, this bloodline is hidden away, their power kept strictly in check so as not to be noticed by outsiders in any way. The Titans will return to save this world, they say, from the excesses of the gods, guided by the Titanborn who are to teach them the errors of their past. The Titanborn await this day eagerly, festering impatience with the gods who do not justly serve. Only the gods who know kindness and serve justice will be spared the wrath of the Titans, the legends declare, and when the Titans rise, the gods will be consumed again if they defy them.

Monks who train in this style learn to transform themselves in potent ways as they advance in their arts. They can shrink and grow their own bodies, grow additional arms or dangerous weaponized appendages such as scorpion tails. They strike more often and can whirl through enemies with their special footwork techniques that make them excellent hit-and-run attackers. At their apex, these monks can assume the traits of various monstrosities and giants, using potent transformations to assume a powerful combat form.

Alter Body

3rd-level Way of the Titans feature

At 3rd level, you learn to change your size to your advantage. As an action, you can cast Enlarge/Reduce on yourself without expending a spell slot. You must concentrate, as if concentrating on a spell, to maintain the benefits of the spell. You can cast this spell this way a number of times equal to your Wisdom modifier (minimum 1) before you must finish a long rest to cast it this way again.

Additionally, you transform your hands (or feet) at the moment of impact to improve the damage you inflict with your strikes. You may add your Proficiency Bonus to your damage dealt with unarmed strikes or melee monk weapons once each turn.

War Form

6th-level Way of the Titans feature

At 6th-level in this class, you learn a prodigious combat transformation which makes you a terrifying force to confront in combat. Whenever you cast Enlarge/Reduce on yourself, you can additionally choose one of the following transformations:
Additional Arms. You grow two additional arms from your torso for the duration of the spell, and you can use these to take one additional attack action on your turn for the duration. Also while you have these arms, you may use one extra reaction before the beginning of your next turn, if that reaction is used to make an Opportunity Attack within your reach, but no creature can provoke more than one Opportunity Attack from you at one time.
Centaur Frame. You change your legs and lower body to resemble a beast's, gaining two more legs and much more speed and stability for the duration of the spell. While you have these legs, you gain temporary hit points equal to your Monk level, +10 speed, and you have advantage on saving throws against all spells or effects that would move you from your space against your will. 
Dangerous Tail. You grow a long tail for the duration of the spell, which may be used to attack and grants you amazing balance. As a bonus action or an attack action on your turn you can make a tail attack as an unarmed strike, which deals 1d12 + your Strength or Dexterity modifier damage, your choice of bludgeoning or piercing damage chosen when you transform. While you have this tail, you have advantage on all Dexterity (Acrobatics) checks.

Metamorphosis

11th-level Way of the Titans feature

At 11th level, you gain the ability to change your body fully, whether for additional forms in battle or for more utilitarian ends. You can cast Polymorph on yourself without verbal and material components, and without expending a spell slot. You must maintain concentration, as if concentrating on a spell, in order to maintain these benefits on yourself. You can cast this spell this way a number of times equal to your Wisdom modifier (minimum 1) before you must finish a long rest to cast it this way again.

Perseid Form

17th-level Way of the Titans feature

At 17th level in this class, you discern one of the most powerful transformations the Titans utilize in battle, emulating the destroyer Titan Perses in combat capability. You can cast the Tenser's Transformation spell on yourself without verbal and material components, and you must maintain concentration, as if concentrating on a spell, to maintain the benefits of the spell. When this spell ends, you have advantage on your Constitution saving throw forced by the spell. You can cast this spell this way once before you must finish a long rest or spend 5 ki points to cast it this way again.

Additionally, if you are concentrating on Enlarge/Reduce or Polymorph, you can cast Tenser's Transformation and maintain the benefits of your previous transformations for as long as you are concentrating on the Tenser's Transformation effect.