Availability of Siegebreakers

Are Siegebreakers available in Chests or are they only available in the shop of the appropriate Event?

During their initial event, they are not available in chests or any source other than the event shop.

After their event, they enter chests like any other normal troop in about a month. This includes the glory/gem/vip general pool that has everything, the possibility to be in summoning stones or random drops from other shops that meet their criteria (eg., random x color troop, random x kingdom troop, random x race troop from ToD/Raid/Invasion respectively) , and event chests when that kingdom rolls around again.