WARNING: The following contains spoilers for Season 1 of Trese, now streaming on Netflix.
In Netflix's Trese, Alexandra spends most of Season 1 trying to live up to her father's name. Anton was a legend in Manila, helping bridge the supernatural and human realms while becoming a Chosen One of sorts after living in both worlds. It's why even the cops have respect for him, especially Captain Guerrero, as they know he seeks the best interests of both parties.
However, thanks to Talagbusao, the sinister god of war, Alexandra finds out her father had a very sinister side to him, and that he's been manipulating everyone with a dark secret in order to maintain a balance.
Talagbusao was banished by Alexandra and Anton years ago as she first cut her teeth in the trade. She was angry that monsters from the underworld had killed her mother, breaking the accords Anton set up, so she jumped at the chance to take the war god down. But when Talagbusao returns, he reveals key intel that shatters Alex with some news -- she's not the only child of prophecy.
Death courted Alex to be queen of the underworld someday, but she fought back against that mission as she didn't believe in mystical prophecies. But Talagbusao shares insight into her father Anton's past, which included visiting the shamans in the mountains. It's where he found his wife Miranda, a seer, but amid the relics and gifts, he also discovered a massive secret about the twins they were having.
That's right -- Anton kept Alexandra's twin a secret as he'd unlocked a prophecy stating one child would pass judgment on the world, while the other would destroy it. The former is Alex, but to ensure the latter never came to pass, Anton used a ritual to kill and convert the other sister into the family's talismanic blade. In addition, he altered the prophecy, using it to then influence the underground and shape the accords. It was meant to keep peace and stop the destruction of the planet.
However, this is why civil war broke out when Alex went on her own spiritual journey into the Balete Tree. Some monster gangs discovered Anton's shady rewriting of history and wanted the accords broken. This battle was fierce and eventually cost Anton his life. As a result, when Alex returned years later in Trese, she began embedding herself more in violence.
This turns out to be Talagbusao's trump card. He knew all along humanity's thirst for blood would summon him out of his prison, and now he'd be able to raze the world. That's why he's been using gangs to cause havoc -- he wants to convince Alex to pass judgment on a chaotic Earth, so he can fulfill the role her sister was meant to take on.
Talagbusao simply used Anton's deceit to leave his own sons behind for Alex to care for, knowing they'd be his eyes and ears, inadvertently helping the villain plot and lay this intricate trap. Had Anton come clean, maybe Alex could have patched up new accords and prevented this, but alas, the sins of old have come home to roost in Trese, leaving her wondering what else her father has hidden.