I see you listed /Mu
That is referencing Patron Pool Powers from Redside
https://homecoming.wiki/wiki/Patron_Power_Pools
You gain access to them by completing the entire story arc or just its final mission.
Both will often be seen in LFG.
You can earn badges by completing the entire story arc or the arc's final mission.
https://homecoming.wiki/wiki/Villain_Accolade_Badges
*NOTE: All Patron badges may now be earned by a single character. However, only one patron contact may be chosen per character.
meaning only ONE patron pool may be selected.
Blueside happens automatically
https://homecoming.wiki/wiki/Ancillary_Power_Pools
Each AT has slightly different Pools, so it is worth looking at the wiki to see what is available to you and how each pool could benefit your build.
*Ancillary Power Pools, also known as Epic Power Pools, become available to hero-aligned and villain-aligned characters at level 35. Additionally, Patron Power Pools open at level 35, but require doing a Patron arc to unlock, so only characters of villain alignment can unlock these pools (though they stay unlocked for that character regardless of alignment after unlocking). A character can only select one Ancillary Power Pool or Patron Power Pool on a particular build.
You can change your pool choices during a respec.
Pools are optional, but they can be beneficial in filling in specific areas in your build that you feel are lacking.
It is important to note that Warshades, Peacebringers, Arachnos Soldiers, and Arachnos Widows do not get access to Ancillary Power Pools.