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How many points should the list be? That will determine if it is viable.
I am right 94% of the time, why worry about the other 3%.
off the top of my head.....
regular Stegadons- it pays to put a skink chief onboard one with the Stegadon WarSpear- yes it costs you your 50 points in magic items, but it doubles your stegadon's impact hits from 1d6+1 to 2d6+1 (or 2, don't remember), plus they count as magical attacks; plus it counts as a spear so your skink chief will also hit with a S6 on the charge....quite a substantial return on a 50 point magic item.
Ancient Steggie- use a Skink Priest on it, not a chieftain. The points you spend on a regular steggie vs an ancient one is not worth the return in points. A priest with the Engine of the God's is what you want on it.
Remember that a steggie or ancient steggie as a mount does not count against your special or rare unit choices.
at 2250, well it depends if you are taking a Slann or not, to start. I would personally, they are too good not to have.
I'd go with 1 ancient with a priest and 1 regular steggie with a chieftain.
You still have room for one more character- if you are going up against a magic strong army you probably want a second priest for scroll caddy purposes. Otherwise you can take an additional steggie.
Remember that if you were to field 3 steggies, you won't need as many saurus and can use skinks to make up for the missing massed troops to both speed bump and skirmish purposes.