Training from Medrengard
Starting when you choose this tradition at 3rd level, you become proficient in Athletics (or another skill in the Monk skill list if you are already proficient) and can manipulate your body's ki in order to channel it's power in amazing physical feats. You can always use your Wisdom modifier when making an Athletics check.
Iron Warrior Technique
Also at 3rd level, you also gain the ability to channel your ki into powerful techniques. Once during your turn, if you are not wielding any weapons or shield, when you replace an attack roll with an Athletics check to Grapple and successfully grapple your target OR when you hit an unharmed strike attack against a creature grappled by you, you may spend 2 ki points. If you do you can use one of the following Iron Warrior technique :

Takedown : You swiftly bring your opponent to the ground in a thunderous takedown. Roll your Martial Arts die. The target takes the total plus its Strength bonus in Bludgeoning damage. You may then move the target to any point within your reach. The target is knocked prone.

Limb Lock : You bend your opponent's limbs and reduce their combat effectiveness for a moment. The target is forced to drop whatever it is holding in its limb. You may choose the targeted limb when you attempt the lock. If the target is also prone, roll two times your Martial Arts die. The target takes the total in bludgeoning damage.

Throw : Using deep knowledge of combat balance, you throw your enemy away, breaking the grapple. The target is moved by half the maximum of your Martial Arts die times 5 feet away. It and any creature of equal or lesser size it goes through is knocked prone. If the target moves to a object of a significantly higher weight or size (like a wall or a bigger creature) it stops its movement.
Iron Within
At 6th level, your mastery of ki flows vibrates through your skin, dramatically increasing your physical prowess. Your proficiency bonus is doubled for Athletics and the damage done by your Iron Warrior Techniques count as magical for the purpose of overcoming resistance and immunity to non-magical attacks and damage.

You gain the additional Iron Warrior Technique.

From Iron, Steel : By crushing focus points in your target, you feed off your it's inner balance. You gain Temporary Hitpoints equal to a roll of your Martial Arts die plus your Wisdom modifier that last until the end of your next turn.
Iron Without
At 11th level, your mastery of your inner ki allows you to control your body with efficiency. You have advantage on grappling contests with creatures your size or smaller. When you succeed a grapple check on a hostile creature by 10 or more, your energy resonates with its killing intent. You no longer need to spend Ki points to use Iron Warrior Techniques on this creature for an hour.

Hammer of Olympia
At 17th level, your mastery of Iron Warrior technique is so advanced your flesh begins to blend seamlessly with ki. When you use an Iron Warrior Technique, you can spend 2 Ki Points to empower it. This increase you Martial Arts Die to a D20 when using this technique.

Additionally, you can externalize your ki to manifest outside of you like a colossal armor of steel, increasing your size and power. Once per long rest, as an Action, you can spend 3 ki points to use this feature. You immediately cast the Enlarge spell on yourself without using a spell slot or it using your concentration and you gain resistance to all slashing, piercing and bludgeoning damage while under the effect of this spell when cast this way. You can end its effect early by spending a bonus action.