That Time I Got Reincarnated as a Slime, Vol. 18 (light novel)

The seraphim army-s invasion under Michael-s command moves forward, and the Walpurgis Council is held for the eight demon lords of the Octagram to respond to the threat. Veldora-s eldest sister, the true dragon Velzard, has fallen into the enemy-s hands through Michael''s skill Ultimate Dominion. Rimuru will need to deploy Tempest''s military to various places if he hopes to rectify this situation...