Before we talk about base building, you need to unlearn every habit from standard Ranger play. Calliope is a with the following base stats (un-upgraded):

This is the ultimate philosophy: You aren't building DPS; you are building time . Calliope buys you infinite time.

Do not put her on the wall. Put her behind the wall, in a second-layer bunker. When the Spitters destroy the first wall, they will flood in. Calliope will fire down the corridor, piercing through 10 zombies per second.

Doubling down on her natural gift allows her to outrun almost everything in the game. This turns her into an elite scout who can trigger a pack of zombies, lead them into a choke point, and escape unscathed. Critical Hit Chance:

: Never stand still. Shoot, move back, and shoot again. This maximizes the distance between her and the horde.

Use Calliope to pull "aggro" (attention) from a horde, leading them into a kill zone occupied by Soldiers or Snipers .