Overlord Blackout is Blackout's second half. He appears to be on a similar power level to the normal Blackout, but does not hold back as much as our normal Blackout does. Unlike most individuals on this power level, OB does not try to kill his other half, since they're both the same individual and killing one would result in the immediate death of the other.
Battle of the Halves/Alternates
OB's first known appearance was during the Battle of the Halves/Alternates, when Ynot threatened to unleash Hollow Ynot on Blackout. Blackout responded by letting OB come out and play, and come out and play he did. He blasted Ynot out of Darkmount, smashed him into the Earth's surface with a Nox Energy-charged asteroid, and then flew into a city at high speed, destroying some of it.
Blackout and OB then took on Ynot and HY, using lots of silly combo attacks on each other, sending the International Space Station back in time, crushing Belgium with an asteroid, ruining two city blocks, and stabbing the Ynots with eclipse daggers. Then Blackout had the idea to create a crack in time inside HY's armour, which began to suck in both Ynots, and the Blackouts too, since Ynot decided to take them with him.
They ended up in ancient Japan, and had a sword fight, until suddenly the Shattered Mirror Universe version of Atlantis crashed next to them, and a lot of weird beings walked out. And everyone was teleported to Mahri Nui, where Ynot fried many sea Rahi with lightning, and then to Z'traa, where the Blackouts began murdering Vrai, only to be stopped by the Ynots, and then by the detonation of the Vrai bioweapon by Xeno. Hollow Ynot then asked if everyone could go back to their time and place of origin, to which OB responded by suggesting the use of a reverse time-bubble generator to "put the bubble in reverse", and also kill HY as an unfortunate side-effect. The Blackouts then suggested a vote, which they won by preventing HY from voting against them. However, they then ended up on the Dalek Crucible, during the reality bomb crisis, which Ynot apparently wasn't around for.
Ynot then pulled out a Memory Seal, sending himself back to Darkmount, but also sending the Blackouts back by accident. The battle could've continued there, but then Zev Raregroove arrived, captured Barricade, and took all the good guys away with him. Then Caiaphus created a huge black hole, prompting Blackout to seal OB away and activate the Conduit, turning himself and everyone else nearby into hyperdimensional beings.
The Uterio War
OB made another appearance during the Battle of Neo Z'Traa, where he helped Blackout fight a gigantic Pokemon called Regigigas. After someone called Osseron had shown up and blown up Regigigas, the Blackouts started fighting Groudon, Kyogre and Rayquaza. However, OB got bored of fighting Pokemon and decided to help Perseus in his fight with Uterio di Armechio. The two then pummelled Uterio, severely injuring him and causing him to fall into a coma.
During the Battle of Corrantia, he and Blackout made an epic entrance and then started killing random people.
Then the random soldiers fired missiles at OB's heels, causing antidermis to leak out. He then teleported away.
OB's antidermis was placed into a new body with armoured heels, and he joined Blackout in attacking Mordor. During the trip there, OB suggested that their duo be named the Ghostbusters. Blackout obviously said no.
After briefly fighting Uterio, OB teleported away and started fighting random mooks. A DOG mech appeared and shot at OB's heels, but the shots bounced off and OB punched through the DOG's armour before going back to killing random mooks. While he shouted at the Toa Yerta, a Dalek burned a hole in his armour. OB killed it, but was then attacked by ten more. After destroying them, more Daleks attacked him. However, the normal Blackout helpfully threw DOGs at them, which OB found odd. He then teleported over to Nadle, who told him to provide cover fire for a medic. OB asked if this was a useless task intended to keep him occupied, and then started bombarding the lower east side of the battlefield with shadow balls.
After Uterio was stripped of his power, most of his troops deserted, and was forced to run away, OB disappeared into a portal along with the other Blackout.