Ancient Construct

Overview
The Ancient Construct is a boss in 2.2 Patch. The Construct can quickly wipe out a group of Heavy Tanks with its laser attacks that almost ignore armor. It is also immune to stun effects, and highly resistant to all damage except explosive.

That's the bad news. The good news is that the rewards are quite worth the trouble. The Sinister and Dexter Fragments which might be won can be very useful. It's worth noting "Sinister" and "Dexter" are old words for "left" and "right" respectively.

Rewards
After defeating this monstrosity one can obtain:
 * 1-2 Laurels
 * 1-2 Widgets
 * Sinister Fragment (Unit), 5% drop rate
 * Dexter Fragment (Unit), 5% drop rate
 * 1-2 Widgets
 * Sinister Fragment (Unit), 5% drop rate
 * Dexter Fragment (Unit), 5% drop rate

The Construct respawns, making it possible to battle it repeatedly to try for the Fragments. The respawn time is 168 hours (seven days).

Strategy
Players have found several strategies that work to defeat the Ancient Construct. There are a few things to keep in mind before trying any of them, however:
 * You will suffer casualties, even if you win.
 * There is a big luck factor. No strategy is 100% reliable.
 * You will probably need to be level 35+ and have troops at rank 4 or higher to have good odds of victory. This battle is available to players far too low-level to win.

A common strategy

Clarified and more specific "common" strategy by luxionmk2