1) 50 crystals
2) 25% of the army
3) a dragon artifact
or
4) fight 300 Archangels
Added 4 minutes later
How many cities does the Yellow Player have in the 2nd mission, and how can I reach them? I've only found one so far, but I can't reach it because of the wall of fire and 2 stacks of monsters (1st stack consists of hundreds of Devils and their upgrades, 2nd stack consists of the same number of Bone Dragons and their upgrades).