Choose armies to an agreed point total.
Set up terrain then roll for random deployment zones.
Roll to choose deployment zone, defenders set up first.
The Tyranids are the attacker and get first turn.
The mission uses variable game length.
The Tyranid player wins if there are no defending units on the field at the end of the game.
Units that are falling back or in reserve are at the end are not considered for victory conditions.
Mission Special Rules
At the start of the turn, the Tyranid player forms her destroyed units into squads. These squads may be deployed with a different size than they started with, but must still conform to minimum/maximum squad sizes. Then the Tyranid player rolls for each squad. On a 4+ that unit is placed anywhere in the Tyranid's deployment zone or into ongoing reserves if desired.
Then rolls for reserves (if any) are made as normal.
Next up, a Tyranid Attack BatRep
The Hive Hungers
And is Coming For Lunch