Yeah, Orchid prepped his harpoons (currently 2/3) for this. I'll give it another shot on my next turn. Question though, is there anywhere on the keep that Orchid could throw his harpoon and then scale? I'm going to guess the dragon wants high ground and is going to cheese us from the top of the tower. RPG logic tells me we must then climb up the stairs to reach the dragon, but Orchid is a Totem Warrior. Thus, he'll climb from the outside, scaling via harpoons until he can reach the dragon.

Also that should be a +5, not a +3. It's STR+Proficiency (3+2), right?