Depending on your DM's interpretation of the rules, Rainbow Servent, in CD is either the best thing a Warmage can take, or an utter waste of 10 levels. Its capstone ability grants access to ALL CLERIC SPELLS... but, it doesn't specifically say they're added to your list. A nice DM (like mine) takes this to mean that a Warmage/Rainbow Servent can spontaneously cast every single spell on the cleric list; a mean one rules that you get nothing from it at all.
Sand Shaper is similarly good, and far less ambiguous, adding a goodly number of buffs and summons to your spells known (its exact words) at the very first level.
Sand Shaper is similarly good, and far less ambiguous, adding a goodly number of buffs and summons to your spells known (its exact words) at the very first level.