2500 points, i may be a little bit over, ill try to some points out. Slann Mage-Priest. Lore of Metal. 4 Disciplines: Healing (hell cannon), Rumination, Mystery, Becalming Cogitation. Cupped hands of the old ones. Bane Head. Skink Priest. Ancient Stegadon with Engine. Level 2 Upgrade. CoD. Skink Priest. Ancient Stegadon with engine. Level 2 upgrade. Rod of Storm, Blood Statuette. 20x Temple Guards. Halberds. Plaque of Dominion. 18x Saurus Warriors. Spears. Banner. 18x Saurus Warriors. Spears. Banner. 15x Saurus Warriors. Swords and Shields. Banner. 1x Ancient Stegadon. 1x Ancient Stegadon.
Unfathomable presence probably isn't necessary, as becalming cogitation should protect you from any irresistable force casts. Trade that discipline for cupped hands of the Old Ones. You could actually take out the enemy's mage if you miscast just right and then pass it to him. The two ancient stegadons you have in rares can't be EotG, they would come with two blowpipes.
wow. 2 EotG and 2 A. Stegs, plus 3 fighting blocks? i think this is more than a good army to take out warriors of chaos. but i don't think you need this much power fighting them. usually a slann with 1 EotG is plenty to take out Chaos. i'm not sure if your opponent is going to have much fun playing you. lore of metal is all you need to take them out. you could bring the slann with 1 EotG and 1 skink priest and give both the priest rod of storm and allow the slann to roll for spirit of the forge like crazy. this should be enough to take out anything coming your way. but if you're going with this list, then have fun blasting them away. also, you're over by 503 pts.
Good for your first list Should be a massacre, now you just gotta hope he has enough fun to come back for more.