http://i.imgur.com/XrykC6l.png
Just for fun, there you go. Completed game, 100%. The maximum level, it turns out, is 99, so we got there. Full legendary equipment, >20,000 of every skill, and beating the entire void in ~50 seconds(~1 minute 30 seconds to kill every enemy.) Fun game. Side-note though: There isn't an upgraded version of the cross or sweep spells, which is weird.
If anyone wants to know what's probably the best strategy for normal fights: get all archers. Ideally longbow archers or fire monks/archers. Your hero blocks the enemies (use defense/champion tactics whenever possible) and your ranged units almost never die. I've been winning most of my battles without any units dying (other than hero, of course.) Hell a couple I never got anything hit. Downsides? The beast becomes very hard, Pestilent is much harder and Death is just derpy and awkward.
To touch on ayala123's comment, 150 score isn't really any. The next quest is for 500 anyway. Considering you can play arena and get many thousands in a day, and I as a pretty casual player have 121000 score. People I know have 2 million.
lol @Dedwynde with the objectively incorrect everything.
1. Strategy is involved, it's how people with okay collections beat people with great collections.
2. Gems are constant, you can easily get 300 gems per week every week throughout the entire game, which is more than enough to allow 5 or so of the top 20 players in the entire game to be completely Free to Play.
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 "Monster Clearer"){kind=icon}
 "Monster Legions"){kind=icon}
 "Elements"){kind=icon}
 "Castle Wars 2.5"){kind=icon}