Now that the Dragon Amulet is properly prepared, go back to the Ancient Ruins. Use the Dragon Amulet with the Hugin Gem at the summoning stone (the large circular platform), at the south side, to summon Ari. It's time for Skarin to make good use of his seizures anyway.
When Ari shows up, there will be a brief tutorial of what dragons can do during mass attacks. The usual subscreen will be replaced by the Eye of Asgard, which provides an overhead view of the field. From here, special ammo-like items called dragon runes can be spent to have the dragons instantly kill available targets. For now, choose either of the targets offered and see how this all works out.
By this point, Skarin should be ready to lead the last major battle for this island world. If he's still lugging around any kegs of mead, he should drop them off with the innkeeper now. He may also want to grab as many special attacks as he can from the local arena, because the next arena won't be available for a long while.
"War is where the young and stupid are tricked by the old and bitter to kill each other." - Niko Bellic