your mastery of the potential brings out its strengths, you gain the follow while wielding a reach weapon 

• While wielding your weapon, creatures you choose suffer Difficult Terrain while within your reach.

• when are creature enters your range, As a Reaction you can make an Attack of Opportunity. Regardless if it hits  the creature loses half its movement. Furthermore you can make an additional attack as part of the reaction if they press into 5ft of you. Using the pommel attack listed below

• when a enemy in in 5ft of you. You Gain +1 to your Ac & can make a bonus action 1d4+str pommel attack. However you can not attack with the main die of the weapon(eg blade) until you are 10ft from them.
• your polearms gain the fitness and versatile properties suffering a -1 to hit weilded this way