- There is now an entire extra tier, the Advent Prototype Assault MEC, which can show up as early as FL 10. It does not have Phase Shot (it just fires standard shots with its shotgun), and features less HP, Armor, upfront damage and shredding than its Military bigger brother.

- Weapon damage has been increased.

- The original version of Phase Shot has been swapped for a cloned version that lives in ABB Perk Pack. This one has a hard range limit of 6 tiles, so they'll only use their shotgun up close. Likewise, the Prototype variant has a cloned, 6 tile limit version of Short Shot for similar purposes.

- Their shotguns now use LWOTC's shotgun range table.

- The Military variant now gets the Tactical Sense, Basic Intrusion Guard (+60 Hack Defense), and Open Fire (Favid's version) abilities.

- Both variants get the Charger ability (MEC Troopers ability, so they won't have this if you don't use MEC Troopers; it increases their Mobility by 4, bringing them up from 10 Mobility to 14).

- AI has been overhauled. They value moving with their first action more, as they can't fire multiple times per turn. The only time they won't move is if they already have targets lined up for Gatling Sweep. They will always prefer to fire their shotgun, if they're within 6 tiles, rather than their Gatling Cannon (although Phase Shot has a global cooldown of 1).

- Both tiers drop their own corpse (Advent Assault MEC Wreck). This has its own breakdown research as well. This breakdown requires Advent Robotics research to be completed first. The corpse is worth 12 Supplies.

- Two new weapons for XCOM: the Prototype Assault Shotgun (Mag tier) and the Elerium Assault Shotgun (Beam tier). These are shotgun-style weapons for SPARKs and MEC Troopers. They can take weapon attachments, use special ammo types, and do more damage, have more crit chance and have a bigger magazine size compared to the equivalent tier Autocannon, but also use shotgun range tables making them ineffective at longer ranges. The Beam tier also does not Rupture, and neither version gets the Phase Shot ability (they just have regular Standard Shot and Overwatch). The Prototype variant costs 30 Supplies, 2 Alien Alloys, 1 Elerium Dust, and 1 Advent Assault MEC Wreck to build, and is unlocked by Gauss Weapons research and the Advent Assault MEC Breakdown. The Elerium variant costs 60 Supplies, 4 Alien Alloys, 6 Elerium Dust, 1 Elerium Core, and 1 Advent Assault MEC Wreck to build, and is unlocked by Heavy Plasma research and the Advent Assault MEC Breakdown.

- One new Render tech for the new wreck, which breaks down for 6 Alien Alloys, same as a Bio MEC Wreck. The wreck has also been added to the Steal Corpses Covert Action, at the same tiers and with the same drop chance as Bio MEC Wrecks.

- Both variants have been added to the VALID_FULLOVERRIDE_TYPES_TO_TRANSFER_TO_OUTPOST list.