LA Caelum is a really cool nation imo.
You've got death, earth and air. Their path's would be theoretically good for thugs, but they lack the power to survive melee.
Their is however a trick ... twiceborn and kill him.
Some other ideas (Try it in a SP game before using them, though).
Aim - Shadow Blast - Shadow Blast - Cast Spells
(preferably with Eye of the void and spell focus) from d2 harabs with 5 guards and 5 decoys. A highly mobile force that should be able to take undefended (i.e. PD only) provinces.
Summon Lammasthas, retreat - practically the same only that you have to fly in a scout the turn after to claim the province.
Summon Earthpower - Rain of Stones
against large human armies. Couple it with Life after Death, Marble Warriors and/or Fog Warriors to protect your own stuff but try to not have a large army there when using it. Unless you want to make your researchers undead (saves upkeep).
Bane Lords + hammer of the mountains + lychantrope's amulet + girdle of might
And someone to cast Earth Grip/False Fetters with Eye of Aiming/Aim should work against SCs.
Don't forget Skull mentors for research, I've made that mistake in my first MP game.