Complex sentence: But in the Varia arc, Lambo plays a bigger role when he is chosen to be the Vongola Thunder guardian by Iemitsu Sawada and is given one of the Half-Vongola rings.
Split into simpler sentences: But in the Varia arc, Lambo plays a bigger role. Lambo is chosen to be the Vongola Thunder guardian by Iemitsu Sawada and is given one of the Half-Vongola rings.