Two teams, a timer and an air horn.
Teams are placed on opposite sides of the field. In the center of the field there's an air horn.
It's a game of elimination with one simple exception: each team has the option of bringing back their players from the dead once by blowing the air horn. Team 1 brings their teammates back by blowing the air horn once and team 2 blows the horn twice. Choose a time length that's good for your field size and the number of players involved - twenty minutes is usually about right.
The team with the most players left when the time is up wins.
A good team plan is key to winning at Necromancer. Do you blow the horn at the first or do you risk not even getting to the horn as time runs out? Do you surround the horn and prevent the other team from ever blowing it or do you ignore the horn and just focus on eliminating the other team early on? Whatever your strategy, just make sure your whole team is on board and you work together.
Only allow the first team to get to the horn to raise their dead.
Only allow teams to blow the horn if they get to the horn in the first half of the game.