Kingsmouth has 3 lair bosses: Head of Glamr, Cta-Tha, and Wreathmother. The summoning circles are located at 865,968, 753,957 and 971,865.

Head of Glamr (325k HP) – Has a large AoE and a Rogue Wave chain lightning ability that will gain range with an unpurgeable buff, heals on glancing hits, immune to impair and hinder effects, has increased penetration chance

Summoning Ritual Fragments
Gamma 09	Phi 03	Gamma 05
Alpha 03	Xi 04	Theta 09
Lambda 01	Gamma 01	Phi 07
Assembled Summoning Ritual

Cta-Tha (325k HP) – Has Tainted Brine poisonous AoE that cannot be interrupted, high defense rating, and glancing hits give stacks of Call of the Huskarl buff which cause him to summon allies (Keelhauled, 4.7k HP each)

Summoning Ritual Fragments
Theta 04	Kappa 09	Psi 08
Chi 01	Epsilon 05	Eta 05
Xi 03	Zeta 08	Beta 06
Assembled Summoning Ritual

Wreathmother (266k HP) – Has a Red Sea buff which causes her to self heal at end of countdown, critical hits reset the countdown, has an Empty the Cauldron frontal AoE with a significant DoT

Summoning Ritual Fragments
Lambda 03	Pi 04	Upsilon 04
Rho 07	Tau 05	Xi 05
Rho 01	Tau 06	Omicron 07
Assembled Summoning Ritual

References

http://forums.thesecretworld.com/showthread.php?t=45626