Low power creatures, you say (with the implication to avoid ones that have self-pumpers)? That would seem to suggest Air (best is 13, but not counting the dragon, it's 7), Darkness (12 with the dragon, 7 without), Entropy (12 with the dragon, 6 without), or Light (12 with the dragon, 9 for the nymph, 7 for the next step down).