This number puts together two irreconcillable philosophies: Duality and Trinity. This is the basic conflict between Shadowmasters and Star Gods. Summed up as 5, it represents Totality.
Trinity represents hierarchical universe, a triangle with a fatherly or motherly figure placed at the top, with the power to say what is good and what is evil. The apex is irreplaceable: Satan gets cast off the Heaven and replaced with Prophet. God is the Ultimate Truth.
Duality represents universe of conflict, a circle with no-one placed at the top. The rights and wrongs are a matter of consensus between people, and a pair forms smallest unit. What is good to some will be always bad to some others. Universal values exist since all Life is alike, but the Ultimate Truth remains forever elusive.
As you might have noticed, 23 is also a duality. It's thermodynamics: chaos is stronger than order due to entropy. Thus Shadomasters are laidback in their sacred disagreement. 5 is a symbol of Chaos; but also of Man, and of Magic.