Oblivion constructs are NPC structures in StarCraft II: Legacy of the Void.
When the Terran Dominion, Daelaam, and Zerg Swarm took up assault positions around Amon within the void, he deployed numerous constructs of void energy to combat them. The oblivion constructs were one such construct.
Oblivion constructs spawn around the map, usually when the player is attacking a void chasm or void crystal. They launch orbs of energy at a target point, stunning all units hit by it for 5 seconds and dealing 5 damage every 0.5 second while they are stunned (for a total of 50 damage). The target point is marked, so the player has time to avoid the projectile.
More concerning than the oblivion construct's attacks is that they will heal other nearby constructs and void crystals at a rate of 100 HP every few seconds. For this reason, the player should prioritize their destruction over other nearby constructs.