Gas Output: increase
Build Food: cost reduction
Build Wood: cost reduction
Use him early to do campaign mode, upgrading him to 31. Because Xavis is an economy hero, his skills are passive. Because of this do not reset him once he reaches level 31, but upgrade him no further.
He should be enhanced to +5, which give a +10% bonus to Gas Output, Reduce overall build food cost by -100,000, and reduce overall build wood cost by -100,000.
He can be obtained in Noah’s Tavern