The rewards seem to be too high on general, not just concerning the spins.
Over the course of the day, I'll test the level 0 & 5 areas and comment on problems, if I see some.
Level 0
Earth palace: Antlion & Zircon seem like almost the same deck. I think one has to go, at least out of this very zone, and maybe join another zone with more HP.
Light palace: Twilight's lore would need to be worked on, and it's basically a mono Life (!) with a stand alone Light mark, thus misplaced in the Light starter area. Photon is ok.
Life palace: Rustler is a fine deck, but ridicoulusly strong! With 20 HP, it almost beat my mono Time (6 Nymphs, 6 Dragons, 18 Pillars) The strength difference to most other level 0 decks is ridicoulus. Wandering Peasant isn't weak either, the only weakness comes from its low HP, otherwise it's a boring mono. I don't think that's too good of a deck design.
Water palace: Both are fine
Gravity palace: I already wanted to critize Graviton Recruit, but in combination with Graviton Soldier, they actually make a great couple and RPGish feeling. Difficulty is also fine. Their lore needs a language check though.
Aether palace: Both fine
Air palace: Both fine
Darkness palaec: Both fine
Death palace: See Earth palace - both decks are fine, but they are too similar. We'd also need a new one her in my opinion.
Fire palace: Firebug a bit too strong? Couldn't find it more than once to test more.
Entropy palace: Lycantrophes is really really boring (Pillars not counted, it contains exactly one (!) card - guess which) and quite strong.
Time palace: Only saw my own deck and can't rate that obviously.