Finished the game a while ago, all quests unlocked without any problems, just collect a lil bit of gold, then do the frozen giant once more (with a lil change in the unit composition of course)... less than 5 minutes.
I broke my main rule a while back ("Don't play any new games 'cuz when they get quested, the quests won't work retroactively." for this game; must have been a dry spell between quests or something.
Anyway, I'm happy to report that, like Unleashed, I had no problems getting these quests. Just collected gold and beat the Frozen Giant.
Thanks for proving me wrong, AG! (And for simple quests after the -- ugh -- 3-mutation quest of last week ....)
For the future players - Beer+Lightning=Easy Win. Other classes are not that useful.
A useful tip. The ranged units are especially unnecessary. Vikings are useful for the Great Army quest, but chiefs overpower them.
There is probably a way to incorporate skirmishers and ax-throwers into the battle and it have a positive effect, but the chiefs have brute strength, and the drunks have the attack bonus that can allow them to defeat armies with twice as much health, so that combination may be hard to beat.
In fact, I don't even use the drunkards. After I got Chiefs, I haven't used anything else in my army (only for Skill Flurry) and about 90% of my island passes are wins.
Personally, my opinion is that running one of each unit, then maxing your best(aka chief once unlocked) gives the best build(can allot a tad bit(e.g. 2) more for drunkards). The other units are just there to slow down the pace so that you can recharge your abilities. Order is firebomb, chief, catapult, archers for special abilities, so that they generally recharge for the last fight of the island.
Once you're about 5-6 islands away, it's totally feasible to directly attack the giant(and win). This is where you'll want to pack 7-8 drunkards, and just go raw dps on the giant(activate drunkards before lightning, and it should go pretty smoothly).
Cleared the game with only vikings and spearmen up to the last two islands and the boss island, then switched to thor vikings and smashed the boss. Easy game with perfectly smooth unlocking Quests!
About half an hour more of playthrough, 5/5. Got the Giant with 5 more islands to go and:
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22 Chiefs (lvl 25)
10 Drunkards (lvl 18)
All "spells" lvl 4.
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Total of 5884 HP. Strategy: Drunkards' ability first, then the Thor's Lightning and all spells. I had about 2000 HP left in the end. Managed to cast arrows twice.
@Gogotank Did you use them during a single fight, or during a complete set of fights on one island? Because that's the key... you need to use them during a single fight for the Quest to trigger.
@MrDayCee, I did it in a single fight, not an island, but I didn't get it. Then suddenly while I was battling the frost giant, I got it although I didn't have all of the skills to use. (I didn't have the drunkards)