It sounds like he means to go down there after it.

Celiss considers casting her final spell, but knows that at this point there'd be no point to it-she needs to be difficult to hit, first and foremost. Besides, her improved reach would be nearly useless against this thing-she could only strike at it when it was running away or moving in, not both.

So, Cellis moves down the ladder, stopping above the floor to retain a height advantage, staying in a defensive stance. If the bug-thing is close enough, she lashes out at it.

Spoiler
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Move: Go down the ladder. Stay up to get a +1 to hit from height advantage, if possible.
Note: Fighting defensively, my AC is now 26.

If possible, my attack:
(1d20)[11](-4 fighting defensively, +1 terrain)
(1d6+3)[6]