Taking a break was not an activity Loimos partook in, or any undead for that matter, so as soon as his business in the Emerald Realm was done, he moved to the next thing on his list.
As it stood, now that Emerald Realm was conquered and with the slow pace of progress in expanding undead territory, there was no big mission that actually required the champion's involvement in any way, the other superpowers were not yet touchable, it would simply be idiotic to start hostilities when they could still make plenty more preparations.