18 is low :). Place a terrain die, wait a turn and place another on same spot, then use honeybee honey. And then use your mirror, with +2 boost!
+4 terrain -1 decay +4 terrain = +7
+2 boost = +9
+1 honey = +18 + 2xbase
+mirror (positioned so the +2boost touches it too) = +20 + 2xbase
then place a 4 attack for: ... 28 damage
Use a second honey and it goes to 50+ damage.