What are the levels of experience (grey star shields) for units ?
Every unit get a star at 15, 50, 100, 200, and 400 experience points. 5 stars is the max, and is almost impossible to get to other unit than combat pretenders, champions or very destructive battlemage (Orion, a mercenary, has 1,000 experience points). Every unit gets one experience point each turn (even when doing nothing special — all armies always organize some drill and exercices behind the frontline), or for fighting in a battle (1 xp and +3 xp for winning the battle), and one point for delivering a blow (two swords and quickness is the way to go for experience). You only get experience from melee combat, kills are only useful if you want to advance on the hall of fame. A Champion Skull gives 3 additional points each turn. A commander (+ all his troops) who enters an Academy of War (zero-level blood site) gets 4 additional points each turn. Mindless units never gain experience however.