The Collaborative International Dictionary
Amphictyonic \Am*phic`ty*on"ic\, a. [Gr. ?.]
Of or pertaining to the Amphictyons or their League or
Council; as, an Amphictyonic town or state; the Amphictyonic
body.
--W. Smith.
Douglas Harper's Etymology Dictionary
Wikipedia
Usage examples of "amphictyonic".
The northern, or, to speak more properly, the western Gate, was close to the town of Anthela, where the Amphictyonic council held its autumnal meetings.
The Thebans now availed themselves of the influence which they possessed in the Amphictyonic council to take vengeance upon the Phocians and accordingly induced this body to impose a heavy fine upon the latter people, because they had cultivated a portion of the Cirrhaean plain, which had been consecrated to the Delphian god, and was to lie waste for ever.
Having marched through Thessaly, he assembled the Amphictyonic council at Thermopylae, who conferred upon him the command with which they had invested his father during the Sacred War.
Thus both the Amphictyonic Council and the oracle of Delphi were in their power.