Dominions 5 Wiki

Nets function like any other weapon, except they are, like lances, one-use only. That is, they cause harassment, they can be repelled (length 5 weapon required as nets are length 4), and units with nets tend to waste them on already netted opponents.

Once under a net, a units gets a defense penalty [75% or 100%?], and cannot attack or repel or move. The strength check to get out is rolled against a 19. Size 3 units have a 33% chance of not being affected by then net, size 4 units a 66% chance and size 5 and 6 are notbe affected.

Nets also carry weapon blesses on sacred units.

Source: discussion with the user Arco on discord, and some numbers given by Loggy. Some bit of testing for the nets being wasted on already netted units.