Where you can send those darn illegal aliens back where they came from. With guns. Or else.
Long War 2 is an overhaul mod for XCOM 2, in the vein of the Long War mod for XCOM: Enemy Within. It easily makes the campaign three times longer, if not more, adds in new weapons, classes, abilities, enemies, and lord knows what else, revamps the strategic layer, completely rebalances the game, and cranks the difficulty up to 11, then keeps getting harder.
And it’s free, so long as you already have XCOM 2. Which you should. It’s a great game. You should get it.