The imagery of 2 pillars and the imagery of 3 pillars is closely connected. In the latter the two become opposites for which the third column becomes a balanced alternative.
The Three Pillars are The
Pillars of Judgement, Mercy and Benignity.
Pillar of Water Pillar of Air Pillar of Fire
Left Pillar Middle Pillar Right Pillar
Mercy Benignity Judgement
Capricorn Aquarius Leo
Unicorn Monkey Lion
Sun Divine Perfection Moon
The three lines, or pillars, of the sefirot
Maha Gayatri, Maha Savitri, Maha Saraswati
Birth Life Death