to win lvl 16 epic mode, max time stopper and use melee units. use the spell when the yeti stand at the castle of the enemy. when charge the base. now since your units keep coming it will stand there hitting your units running toward it so it will not attack your base. each time you use the time stopper, you will have some more units attacking the enemy base right under yeti feet where it cannot hit. I think you can kill the big yeti with time stopper (rather than invincibility). would just be the same as killing the lord baal apart from you have to sacrifice units to keep it from moving
anything with non elemental attack (sky dragon, celeste, meteor) can damage the black imp but take into account its high damage and high HP, only a meteor can kill it. any unit will be killed before hittting it the second time (sky dragon will be killed the moment it lands). a lvl 2-3 meteor is best since it can instant-kill the imp. higher lvl require more time to recover mana. use that mana for invulnerability is better.
there should be some warning when the health bar goes low :| i died 3 times because i kept running aroung killing thinking that im too strong :)) use the escape wings a few time you will be way too strong for the creeps
 "Epic War 4"){kind=icon}
 "The Enchanted Cave"){kind=icon}