Solus Christus means that Jesus Christ is the only mediator between God and humanity, and that his life, death, and resurrection are the exclusive and sufficient ground for our salvation. It denies the necessity of human merit, saints, or any other creature as a means of obtaining favor with God.
The principle of Solus Christus asserts that since the fall, humanity has no access to God apart from a mediator, and that Jesus Christ is the only one who can fill that role. As confessed in the 1689 LBCF Ch.22 §2, religious worship is to be given to God alone and must be offered through the mediation of Christ alone, excluding any other intercessors. This truth is anchored in the apostolic witness that there is one God and one mediator between God and man, the man Christ Jesus.
To claim that anything is required for salvation beyond the work of Christ is to suggest that he is merely a 'half-Savior,' a notion the Belgic Confession Art. 22 rightfully rejects as blasphemy. Our justification is not earned through our own efforts, but is received by faith alone as an instrument to embrace the merits of Christ. The Heidelberg Catechism Q.67 confirms that the whole of our salvation depends entirely upon that one sacrifice of Christ on the cross. We are more flawed than we dared believe, yet because of Christ, we are more accepted than we dared hope.