My home region was surrounded on two sides by map edges, and a third by water, leaving only one path for my new settlers to travel: south, through a narrow mountain pass, into barbarian-held territory. I sent them with two shiny new archers and two somewhat-obsolete warriors, for protection.
Except, as I moved through the pass, I discovered the barbarians had founded a town just to the south. The town was size 2 and had a single fortified archer - not a real threat, but too much for my ragtag band. I ignored them and moved past.
A turn later:
a fucking red dragon decides to roost in the town. Strength 29, before promotions and town fortifications, against my strength 3 archers. My small band are now completely cut off from reinforcements (all the nearby forests are on fire, and I don't have any ships yet), deep in barbarian territory. I find a nice coastal spot for my new city - except it's only ~4 tiles from the dragon roost, and is directly adjacent to a goblin camp. Within 2 turns, I'm surrounded by goblin archers (defensive strength 6 + 50% terrain bonus!), and being battered by waves of warriors.
I survive the ever-worsening odds against endless hordes of goblin warriors and archers, before reinforcements finally slip through: my first Ritualist, and a couple of Adepts. The Ritualist proceeds to use summoned Imps to clear out the ~8 archers encamped around my city, finally allowing me to break out and raid the goblin camp, stopping the immediate threat of attacks.
Best of all, I now have a narrow route down the coast, where I can safely explore and possibly expand, and I'm only a tech or two away from transport-capable ships, so I can ferry reinforcements down. Now, I just have to figure out WTF to do about this stupid dragon, since his culture radius covers two different mana-providing unique improvements...
Civ 4: Fall from Heaven II. Oh god, are summoned units ever ridiculous. A pity they waste most of the XP from kills, but still, I never would've held that city without Ritualist support.