The Seized Construct is a boss found in Tears of the Kingdom and is the boss of the Spirit Temple. This is the only boss not responsible for any regional phenomena, as it is encountered after that part of the Main Quest.
Tears of the Kingdom
"The construct that Mineru originally intended to house her spirit. It was changed into this ominous form by the magic power of the Demon King. Originally intended for construction, it is highly durable and able to withstand harsh conditions."
The Seized Construct was originally built by Mineru while she was still alive to eventually house her spirit. Sometime in between her transferring her spirit into the Purah Pad and the present day, it became possessed by the magic of the Demon King in order to prevent Mineru from re-obtaining her Secret Stone within the temple. When [[Link (Breath of the Wild)#Tears of the Kingdom|Link]] has assembled a new Construct at the Construct Factory that comes to house Mineru's spirit, they journey together across the Depths to the Spirit Temple, where the Seized Construct is encountered at the lower floor in an arena completely covered in Gloom. This will require Link to spend the entirety of the fight piloting Mineru's Construct Body, and he will be forced to take gloom damage if it is desired to photograph the Seized Construct for the Compendium.
Upon defeating the Seized Construct, Mineru's spirit re-awakens as the Sage of Spirit from eons past. The Spirit Temple becomes cleansed of Gloom, and two Steward Constructs position themselves on either side of Mineru's Construct, who remains in the temple until the final boss fight with Demon King Ganondorf. The Smithing Construct to the left of Mineru's Construct will sell Link the strongest Zonaite Weapons in the game in exchange for Zonaite, and the Mining Construct to the right of her will provide Link with Ancient Blades in exchange for 50 Zonaite each, as per the Ancient Blades Below trading sidequest.
The Seized Construct is posted in the Depths of Hyrule, being one of many monsters defending the Demon King's location. Link must fight it if he did not fight the Seized Construct in the Spirit Temple, but if he did, then Mineru will deal with it for him, allowing Link to skip this fight.
Unlike every other temple boss in the game, the Seized Construct is not re-encountered in the depths after defeat.
This boss is fought in an arena with an electrified perimeter, and the intended method to fight it is to knock the boss into said perimeter, which deals massive, fixed damage to it. While it's not immune to weapon attacks and explosives, it is immune to arrows by themselves without any fusion. Furthermore, it has an obscene 20,000 HP (even Demon King Ganondorf only has 7500 HP across 3 phases) to dissuade trying to kill it directly with conventional weaponry.
The boss fight against the Seized Construct is essentially a boxing match between the two constructs. There will be various fusable objects and Zonai Devices around the arena, including Spiked Iron Balls, Cannons, and Shock Emitters that can be fused to Mineru's Construct, in addition to the usage of any Zonai Devices in Link's inventory; Ultimately the type of Zonai Devices used in this boss battle is entirely up to the imagination of the player. The perimeter of the arena is blocked off by an electric fence that will damage everyone inside, and the primary way to deal the most damage is to try to knock the Seized Construct into the fence. One way to do this is by using Mineru's Construct to block every time the Seized Construct goes in for a swing, and then hit it three times with either the left or right arm to knock it into the fence. One of the arms has to be fused with a non-shooting object in order for this to work properly; the Seized Construct will use similar tactics to try to knock Link and Mineru's Construct into the fence as well. Doing this efficiently will require Link to pilot Mineru's Construct somewhat aggressively in order to be in close enough range that the Seized Construct will attempt a swing, and to close the distance between the Seized Construct and the electric fence. Another way is to stun it from range by firing at it with a Cannon Zonai Device on one Construct arm, where it can then be hit three times with the other Construct arm to send it into the fence. After enough times, the Seized Construct will lose enough health to commence the second phase.
If encountered in the War in the Depths of Hyrule (go to the final boss early), then Mineru's Construct won't be an option. Instead, Link must knock it back into the side of the arena with his own weapons, or else deal an absurd 20,000 damage using melee weapons. In particular, combining a Soldier's Broadsword (charge attacks charge faster) with any Lizalfos Tail (extends spin hitbox) creates a highly effective anti-Seized Construct weapon that can rapidly stagger, stun and knockback the Seized Construct with fast Spin Attacks; the components of which are readily available due to being dropped by The Demon King's Army.
Regardless, the Seized Construct takes damage from the perimeter in increments of 1/16 of it's max HP. However, it loses 2/16 each time you force the boss into the perimiter, effectively taking 4 cycles to defeat each phase. While this may seem straightforward, while Seized Construct is on the ground, shocked from taking damage, it is possible to hit it back into the perimeter a second time, and this deals 1/16 instead of the prior 2/16, making it possible to deplete 3/16 of the boss' HP in a single cycle, rather than just 2/16. Once it takes this extra hit of damage, though, it will become to knockback until it gets back up and relocates, so the max amount of perimeter damage per cycle is still 3/16, though this does reduce the number of cycles per phase from 4 to 3 if done properly.
At the beginning of the second phase, the Seized Construct will grow two extra arms, and will fuse a Rocket to its back, two Fans to its lower arms, and two Cannons to its upper arms, where it will become airborne and fire repeatedly upon Link and Mineru's Construct. Link can either wait this segment out and block the attacks until the Seized Construct returns to the ground, or he can fire with a Cannon Zonai Device on one Construct arm for a ranged counterattack, as well as by shooting Arrows fused with Bomb Flowers or Shock Fruit. This will allow Link to then follow up with three more swings from Mineru's Construct, after which the Seized Construct will re-fuse the same Zonai Devices to itself and return to the air. Another attack the Seized Construct will attempt is an aerial body slam, which will deal significant damage to Link if proper defense precautions are not taken. If the Seized Construct misses this attack though, it presents another window for it to be knocked back into the electric fence. If timed correctly, the Seized Construct can be hit one more time immediately after being damaged by the fence for a quick follow-up shock from the fence again before it re-fuses materials and resumes an aerial assault. This process can be repeated until the Seized Construct is finally defeated.