  In the framework of the minimal quartet-metric gravity/systogravity, a scalar
graviton/systolon is stated as a universal dark component, with supplementary
manifestations in the different contexts either as dark matter or dark energy.
An ensuing extension to the standard {\Lambda}CDM model is developed. A
modification of the late expansion of the Universe, with an attractor of a
scalar master equation defining an effective cosmological constant, which
supersedes the true one, is proposed. A new partial solution to the
cosmological constant problem is discussed.
