game/KillBox.cs

A game component that acts as a kill volume. When an object with the "player" tag enters the trigger and this instance is running on the host, it finds the PlayerController on the root object and notifies GameManager.PlayerEliminated.

Networking
public sealed class KillBox : Component, Component.ITriggerListener
{
    [Property] public GameManager GameManager { get; set; }

    public void OnTriggerEnter( Collider other )
    {
        if ( !Networking.IsHost ) return;
        if ( !other.GameObject.Tags.Has( "player" ) ) return;

        var player = other.GameObject.Root.GetComponent<PlayerController>();
        if ( player == null ) return;

        if ( GameManager.IsValid() )
        {
            GameManager.PlayerEliminated( player );
        }
    }
}