"I can't stand it, I know you planned it"
The enemy are up to something and it's up to you to stop it.
Place one objective marker at the centre of the table.
One player is designated the attacker and one the defender. Both select an army of equal value using the standard FOC.
Both players roll a D6 and whoever rolls higher selects either of the short board edges as theirs. The defending player deploys first and must deploy all of his HQ and Troop units within 12" of the objective marker. All other units are placed into reserve. The attacking player deploys 1 HQ and 2 Troop units within 6" of their board edge (NB for this mission a Troop selection and any dedicated transport they may have count as one choice). All other units are placed into reserve.
All units in reserve are rolled for as per the rules on page 94 of the Warhammer 40,000 main rule book. The attacking players reserves enter on via their board edge. For each defending unit entering by reserve roll a D6, on a 1-2 that unit enters play via the long board edge to the player's right, on a 3-4, they enter play via the long board edge to the player's left, on a 5 they enter play via the player's short board edge and on a 6 they may enter play via any of these three edges.
The attacking player rolls a D6. On a roll of 2+ the attacking player goes first. On a roll of a 1 the defending player has heard the attempted sabotage and steals the initiative.
This mission uses variable game length as described on page 90 of the Warhammer 40,000 main rule book.
At the end of the game you control the objective if there is at least one of your scoring units, and no enemy unit within 3" of it. Always measure this distance from the centre of the objective.
Designer's note: this is meant to be a very narrative mission and the idea is that something very important is happening at the objective. Maybe it is an attempted daemon summoning and if they manage to control the objective for 3 full turns they manage to bring on a daemon as a reinforcement. Or maybe it is the control pad for a missile relay and for every turn someone controls the enemy they get to fire an orbital barrage at the battlefield. Or it could be an injured high ranking officer that they are attempting some triage on. It's entirely up to you.