Hollow Keep

Fifteen waves walk a torchlit road toward your keep. You spend gold on five kinds of tower beside it — archers, a frost well, an arc coil, a bombard, and a beacon that makes everything near it hit harder.

The part that makes it a decision rather than a shopping list is that every tower keeps its own experience. Kills feed the tower that made them, so a post sitting on a bend where enemies bunch up will outgrow one you tucked away in a corner. At level three a tower is ready to specialise, and you pay to commission it: an Archer Post becomes a Marksman that punches through plate, or a Repeater that shreds crowds and barely scratches armour. Ten specialisations, and none of them are reversible.

The enemies are built to punish a one-note garrison. Ironclads subtract a flat amount from every hit, so a fast weak tower does almost nothing to them. Coursers shrug off most of any chill. Wraiths fly straight over the road and ignore your bombards entirely. Wardens carry an energy shield that soaks half of ordinary damage and grows back — arc lightning tears it open. A Keepbreaker arrives on waves five, ten and fifteen wearing all of those problems at once.

A session is about twenty minutes. Between waves you build, sell, specialise, or buy back a point of wall, and you can call the next wave in early for a gold bonus that decays while you dither. A first run usually ends somewhere around wave nine or ten, normally to the wardens or the fliers. Clearing all fifteen takes a garrison that answers armour, shields and air rather than one that just does a lot of damage. After that the waves keep coming, and stop pretending to be fair.