Silic is made of something similar to Ruby high heat resistance. Extreme heat is one of the few things that can harm them but it has to be near melting point. Anything short is like breathing hot air on them
Silic is a versatile individual, hard to capture hard to harm and more intelligent than one may give credit for. Also Silic has worked for many of the factions that ‘could’ capture them. Would you lock up your most effective employee?