Concerted Horseman Militia

{1}{w}, {t}, Pay 1 life: add {b} to your mana
pool for each white Knight you control.
{1}{b}, {t}, Pay 1 life: add {w} to your mana
pool for each black Knight you control.
{1}{w/b}, sacrifice Concerted Horseman Militia:
regenerate another target Knight creature.
To save lives, one must also take lives.