Hoo boy....how to defeat Draconis with only half a Mage. Sorry to say this, Jazzybelle, but your party doesn't stand very good odds of beating the game. Still, you never know.
Draconis is a pain in the ass because:
- He's a Dragon, with the AC, THAC0, Breath Weapon and Wing Buffets that go along with that
- He starts the battle with PfMW, and Immunity: Abjuration, so you can't Dispel or Breach the PfMW
- He keeps turning Invisible, which makes him very difficult to target with spells
- He casts lots of spells, including Heal and some low-level summons, making him more difficult to kill
The (best) way to beat Draconis is to cast True Sight, Time Stop, and Improved Alacrity. This gives your Wizard 3 rounds (during which Draconis cannot go Invisible) to pelt him with some Lower Resistances and a horrifying barrage of damaging spells. But since you say that Aerie doesn't have any Level 9 spellslots, that's out of your league. Better use some more Wizard power next time, huh?
As it stands now, your best bet is probably to cheese the hell out of him: Lay a stack of Traps all in one spot, and hope that Draconis steps on it instead of his Invisible Stalkers.