Split top post into 2 and updated formatting:
Worldline Zero Catalyst
The Worldline Zero Catalyst is progressed by getting a hit with a Swing on the Level 7 boss. It is RNG and either a Crit or Damaging hit (Proof below). This progresses the Catalyst by '20%' so must be done on each EP boss over the course of 5 weeks. It is NOT progressed by 5 crits on the same boss / new instance of that Boss
Other Info
If you FAIL after Round 3, you have 60 seconds to restart EP. If you restart here, you start at the Round previous. So Fail at 5, start at 4, fail at 7, start at 6 etc etc
Linear Fusion Rifles are one of the most powerful weapons to use for EP - Proof
You can open the Reward chest for Armour after successfully completing Wave 7 for rewards more than once a week. This can be done via the following:
You are able to carry stacks of the'Encrypted Cache Key' (It appears in your 'Pursuits' tab). Once used, you can visit Ana to create another key using 7 Rasputin Key Fragments
You only able to create '1 key per week' using the Fragments and can only carry a MAX of 7 Fragments.
Ways to get RKFs:
Complete all the story missions in the Destiny 2 Warmind expansion.
Strikes, Heroic Strikes, Heroic Adventures, Nightfall / Prestige, Raid / Prestige and Raid Lairs.
Complete EP, Use Key, Go to Ana and make Key and complete EP wave 7 again for another armour piece. The Blue Key made DOES NOT stack so to open the chest multiple times, you must have previously stacked your Encrypted Cache Keys
If you don't plan on using a Key on the Wave 7 Chest this week, try to ensure you get one charged up and added to your inventory. The Blue version which is charged by completing EP Waves DOES NOT stack but once charged, the Purple version DOES stack. This means you can open the chest multiple times when you get chance
An ideal set up for EP is to have 1 person use the 'Tractor Cannon', a Titan using Melting point and Voidwalker Warlocks to all team up on the boss to really melt it's health. These no longer stack up as effective Post-Forsaken but can be used in Tandem for extra DPS
Hunter Tethers are great for Orb generation to Chain supers. If you hear a Tether go off, try not to kill enemies before they get caught by it (Unless the Tether is a whiffer)
You can find a group for EP by using r/fireteams, the Xbox LFG function, Destiny Companion App and various LFG sites. Alternatively, jump onto Mars and message some folks there or join in one already in progress which is a big + of it being a Patrol instance
The Last Word
EP was a great time during Warmind, for the big groups up to 9 and just the madness throughout each wave and solving the Mechanics, I highly recommend trying it out if you are new / returning to the game and missed it
If it is true that Y2 exotics are farmable here also, you may see a big uptake in Guardians back on Mars running this stuff