Slavery in Goshen takes 3 forms, via Crown Laws.
Indenture
This form is individual, a slave being servant to a master for a set time then eventually released.
Thralldom
This is the first form of population slavery, where groups of people are enslaved for hard labor, though children born in Thralldom are freeborn.
Chattel
This is the pinnacle form of population slavery, with it children born to slaves are themselves slaves.
Thrall and Chattel forms enable the Slave Raid cb so they can fill slave holds in their capital as well as 'honorably' gain court slaves, though less scrupulous individuals can force their prisoners into slavery. This is the only way for Thrall slaveholds to fill.
With slavery comes anti-slavery, realms averse to slavery can use the Anti Slavery cb to lower a Slave realm's laws every 20 years.
Additionally there are several new Flavor items, primarily among them is the Bed Slave decision, which should be self-explanatory.
There were also numerous cleanups and bug fixes.