The insula that Tryggtass lives in was cheap build (as they often are in the rapidly expanding Rome) and fell together. Two young human siblings was caught and shut off in the rumble and wasn't found until Tryggtas heard them and led people there for their rescue.
Gast's burden, the senator, was on a walk through Rome with a few slaves when Gast managed to get a slave to follow him to the crumbled building and as the clever slave under guidance of Gast suggested to the senator to rebuild the house to gain popularity among the people and thereby Tryggtass's burdens was helped in a dire situation. The senator could also run a court process against the rival who built the cheap house and thereby get passed him in popularity and dignitas.
Svansglidaren influences his burden, senator Manuel, to support Gast's burden in the rebuilding of the house and thereby helping Tryggtass's burdens and getting both his own burden and Gast's burden a new ally.