The citizens of Pactasy banded together to fight the evil Lord before he grew; while the armies fought a small band of highly skilled adventurers were sent behind enemy lines to stop the source of the invasion.

(Your probably thinking - 'mmm ... how cliche, this is where I lead my band of adventurers to save the world' - well, you're WRONG!  The current year of this game is 20,008 so the invasion was 500 years ago.)
The band of adventurers failed and the Lord successfully invaded.

Over the next 5 years Lord Cybestos conquered the continent of Crystalis.  This was the largest continent, but it wasn't connected to any other by land.  The nearest continent, Welesham, was  over 500 kilometres away.

Now the Lord had several problems - the denizens of Hell were (and still are) allergic to seawater so they had a hard time on boats.  None of them could fly for more than a kilometre so that was not an option.
His army was now stuck.
Each time an attack was launched it would be thwarted; invasions by sea would be met by wild sea storms that had been conjured up by powerful magic users.

Years later the Lords advisors invented skyships (flying boats) with a range of 500 kilometres, just enough to reach the mountain ranges of Kosciusko.  But  Kosciusko was home to another threat, the mighty Snow Dragons.
These Dragons were Selfish, evil, loners who tortured their prey before eating them; but they were not stupid.  They knew that if the Lord's army invaded Welesham it would upset the balance of nature, this would result in the Dragons food supply chain being destroyed so they knew that it was in their best interests to destroy them before they could land.
Flying boats full of the denizens of Hell were, and still are, no match for a Snow Dragon in a snow covered mountain range.
But even the Snow Dragons realise that the time will arrive when the dark forces of Cybestos invents skyships that can fly further, thus flying around the Snow Dragons.

So as the game stands there is a stand off - Lord Cybestos cannot move his army overseas while the citizens of Pactasy cannot raise a big enough army to invade Crystalis.