i had to add the following to the different factions to turn them into hordes and then changed the units. so far i have only done the western and eastern empires

horde_min_units 60
horde_max_units 100
horde_max_units_reduction_every_horde 20
horde_unit_per_settlement_population 300
horde_min_named_characters 4
horde_max_percent_army_stack 80
horde_disband_percent_on_settlement_capture 33
horde_disband_percent_on_settlement_capture 50
horde_disband_percent_on_settlement_capture 100
horde_unit hun horde spearmen
horde_unit hun horde spearmen
horde_unit hun horde horse
horde_unit hun horde spearmen
horde_unit hun horde spearmen
horde_unit hun horde horse
horde_unit hun horde horse
horde_unit hun horde chosen warriors