Stone of Subjugation

The Stone of Subjugation is an item inside the Aberrant Assault skirmish. It is guarded by an Eye Tyrant, about 3/4 of the way through, just before the final boss.

If you receive a daily skirmish quest asking you to do the "Stone of Subjugation" skirmish this is a bug, but you will get credit for it by completing the Aberrant Assault skirmish and destroying the stone of subjugation located inside that event area.