For Yoshi so we don't get lost of information! To Complete Hidden Objectives you must Do Secondary tasks which then unlock a new chest, get the chest and some drop you Orange Items, those items are hint clues and need to be equiped to unlock hidden objectives. Equip say For example, I Put "Worms" On any hero for item, and then when you get into a battle with one mission that has a hidden objective, Just use the item on the character thats holding it, and if it's the right item to be used it'll start playing "hidden event" and then u'll complete the quest for hidden Objective. Note that it doesn't complete your main objective, so you'll have to restart that mission if it wasn't completed. Some chests give you additional Hidden objective items, I manage to pull a Yellow item that changes your character into a Snake. I'll give away the first one, the worm item tells you that birds would definately eat it!! So when I got to a battle on the Fourth map, first level, there was a Hawk/bird, So then right a the beginning I used the item to unlock the objective. Brought me out to the map so I could get the chest or just go do the quest again for the main objective. Some Secondary objectives can be very hard to complete, always remember.. the more heroes and items you unlock, the easier the the tasks get! Use common sense, if you have to Chase Chests or kill a monster that u can't reach in the beginning, get a Hero like a shaman to give you extra moves Or the Rhino to bump your character to the enemy. I usually use heavy melee assault because you'll see melee more than spells in the first 4 maps Before you start to unlock the mages. Never throw away your gear, always use it or keep it aside, you'll never know because new characters will flush out the items that are not needed, and can be used. Never be afraid to switch off items to benifit the Character, Such index's such as Luck % boost can be very valuable even when it doesn't seem to be. If you have anything else to add in here, feel free to add, this is just a Quick Tip guide you can follow!!
For one Particular Mission yes, but I'm talking about the Treasure chests from the map, hope this info helps
