[atlatea]

Well, you need to replay some of your battles if not most untill your dragon dig a call of colosus.

Not all enemies must be killed asap by the time you arrive on an island. Some enemies are meant to be left untill you reach much higher lv.

Example is the horsemen hero you mentioned, you need at least a red dragon to succesfully kill him without loses if you want to kill him before you advance to rusty anchor or bolo.

If you don't mind traveling forth and back beetwen island, i mean you don't care about the days you spent to finish the game which affect your final score, the faster you finish the game, the higher the score, just use 1 emerald dragon you acquired from rusty anchor and have adrenalin 3 skill (Paladin skill tree), as for spells you must have stone skin 3 or divine armor 3 or both, healing 3, fear 1 or fear 2, oil mist 2 or oil mist 3

Another easy way is to use 1 emerald green dragon, repair droids split to 2 stacks, guard droids. As for spells, it is the same as above, but add target 3, slow 2, haste 2 or 3 to that list of spells. You already use 4 of your 5 slots, 4 slots is usually enough, but if you want to use full slots the final slot is up to you, though i suggest a lv 5 unit especially another dragons (red or black).

After you unlock montero, things will become much much easier, so from this point it's up to you .