Portuguese/Brazilian Draka, let's call them Dracos (better name pending):
- The United Kingdom never disintegrates, or does it later.
- Luso-Brazilian Conquest of much of the Plata follows
- Portugal does not ban slavery and the slave trade in Angola in the 1830s.
- Portugal (perhaps under Dom Pedro IV AKA Dom Pedro I) bans slavery in Brazil (just in Brazil) say, the 1840-1850s. Helped by the fact the Plata is not as slave-dependant.
- The big land owners almost fight a civil war, but then decide to migrate to Africa, to the Angolan Highlands more specifically, as It's still legal there, and it's easier for them to get slaves.
- Driven by expansionism and the need for constant slave supplies, an alliance of local tribes (perhaps with the Kingdom of the Congo?) and slaveholders is formed. The locals supply slaves to the white landlords who mostly live in the Angolan Highlands. Essentially, the portuguese colonists lead, the local allies enforce and the other tribes are enslaved.
- Eventually the Dracos find the Afrikaner republics and build a rapport. Afrikaners let them use their land as bases for slave raids against tribes they don't like and trade with them.
- The Dracos managed to expand all the way from Angola to Moçambique, linking the two colonies and expanding southwards as well.
- The Dracos request the creation of a Fourth Kingdom to the United Kingdom of Portugal, Brazil and Algarves. They are granted and most if not all of Portuguese Africa becomes one kingdom under the United Kingdom.
- More portuguese immigrants come along, they either become part of the lower tiers of society and mix with the locals or join the portuguese slave-holding elite.
- The Dracos run into the Zulu eventually and, considering them a strong warrior people, enlist them into the scheme.
- The British are kicked out of South Africa by Afrikaners and Zulus armed by the Dracos.
- The Afrikaners and Zulus ask for Protectorate by Portugal.
- Technically, Portugal owns most of Southern Africa. In practice, the whole thing is pretty much owned by local potentates allied to each other.
- Eventually the Catholic Church complains, slavery is banned and the Portuguese realize how their colonies in Africa are swiftly becoming one big slave-holding society that barely cares about orders from Lisbon or Rio de Janeiro or wherever their capital is. They decide to put a stop to it.
- By now, the Dracos' white elite has started to integrate with the kings, nobles and chiefs of their african allies.
- An independence war happens where the Luso-Brazilians are defeated, probably with foreign help involved (British angry that the Portuguese got South Africa?). The Dracos put one of their own as Emperor, a mixed-race Draco who has blood from African kings and said blood is used to proclaim royal legitimacy.
- The Dracos, now independent, swiftly start a campaign of expansionism across Africa. Europe barely cares enough about Africa to stop them. They mostly leave the estabilished european colonies alone but do forment dissent and such.
- The Dracos by the 1900s are a nation of race-mixed ultra-slavers. Everyone has a slave. Everyone. Even the slaves have slaves who have slaves.