Another combo I was thinking of would be Evard's Black Tentecles. It summons 1d4+1 per caster lvl tentecles, menaing i'd summon 1d4+12. They all do 1d6+4 dmg and do a grappling attack every round. If I cast it under the dragon, he'd recieve 14(average) tentecle attacks every round plus they'd all be grappling. I was thinking maybe enervation and the sucking touch combo after that. Or maybe just go all out dmg. I could also do spectral hand, vampiric touches.... I dunno, a lot of possiblities here. Lemme know what you think and if you can add to it