Literally: Troll
sex.
To create an offspring two trolls in a relationship (generally red) must offer their genetic material to the Imperial Drones when they come bearing buckets.
If Genetic Material is not offered the two trolls are killed instantly.
The buckets are then taken to the mother
troll who then combines all the genetic material into
one diabolical incestuous slurry and lays hundreds of thousands of
eggs at once.
Trolls hoarding buckets are perverts.