Summoning Region Bosses
Region bosses are special bosses in each region designed for no more than 5 players to summon. The boss is locked to the group that summons it, and any other players will be barricaded from attacking it.
First you must farm (from lair bosses) or acquire the particular 16 blueprint pieces for that region boss and assemble them in the proper position (when positioned properly, the pieces form a picture of the boss). Next, bring the assembled summoning ritual to the summoning circle for that zone (the one with a red glyph on it) and activate it. When used, a heart will appear with an anima link toward you. The other players in the group can accelerate the summoning by moving close to help you.
After successfully using the summoning ritual, the 4 flames of the circle will light, representing 4 tries to down the boss (may be only 3 if bugged). If the entire group dies during a try, the boss returns to the summoning circle and will remain there for 5 minutes, and 1 flame will disappear. When no flames remain, a new summoning ritual will be needed.
When the region boss is killed, it will drop a loot bag containing 2-4 blueprint pieces to summon that boss, 3 epic Bind on Pickup items, 1 epic signet, 1 epic glyph kit, and 1 unique raid puzzle piece.