The final chest in the glacier area should be just behind the guy after the map with your first monolith encounter.You will need 30 medals for that guy to get lost and get that chest in the igloo
Tip:send 3 crusaders(from down to up) at the start of each battle will get you 3 hp off the enemy base 100%.Especially useful in battles where bases only have 3 hp points(mission 9 for example)Also some missions are easier even through they appear later.Very easy missions are 1,3,7,9,10(i get deadly commander the first time playing it)
lv 10 is not impossible,do not stay in the part that make you more powerful for too long,cos it will decrease speed and kill any flying bee you see,to prevent them from reproducing.