Eco construct is an eco power in The Lost Frontier. It is the first green eco power and second power overall that Jak obtains, serving both utility and offensive purposes. It is received from a Precursor idol during the mission "Retrieve velonium power pod", on the path to fight the Uber-Bot 888.
The construct has two uses. The first, a utility purpose, is by standing over a small patch of green crystals and pressing either + (for PlayStation 2) or (for PlayStation Portable). Jak will then summon large green crystals from the earth that allow him to jump and climb to lengths and heights otherwise inaccessible. Most crystals last only a short time however, though always enough to make it across in a timely manner.
It is also possible to use the construct power offensively while not standing on a patch of green crystals, which instead will make Jak cast the crystal a few steps away from him in the direction the camera is facing (or near enemies if upgraded). Jak had to use this power offensively during the Uber-Bot 888 fight, as only the crystal constructs could stop its swinging sawblades attack, also causing the Bot to lose his sawblades in the construct. Eco constructs deals heavy damage to enemies if it hits them, but the short range and fixed location of the spawn makes it relatively useless during combat early on. Both of these flaws can be largely mitigated with the aimed construct shards upgrade, which more than doubles the range and will automatically cause the crystals to be spawned beneath any enemies in Jak's vicinity.
With the expensive construct spike upgrade, which in facts turns the normally pillar-shaped crystals into into thick spikes, the power deals even more damage upon contact. Despite the ease of use and the strength, the eco construct still suffers from the fact that casting a crystal requires Jak to stand still for a split second. This short span of time can lead to receiving damage from an enemy, making it ultimately less useful than it would seem to be.