Missing the 4th Spell, "Lunar visitor" achievement and 'Buy all items from shops'

[Shotgun Justice]

I've got 100% map completion and everything else. Every item in every shop has been purchased. Not sure where to re-tread to find these.

[Hedrack]

Lunar visitor is for a secret boss that gives the 4th spell.

It's in Top City near where you found air dash. There's a monument you need to bomb and interact with the crystal to spawn the boss.

[Hedrack]

Do you happen to have a screenshot of your map? I'm at 99% map and missing a health leaf with no great desire to make another sweep of the map with the secrets familiar to find what room I overlooked.

[Shotgun Justice]

Originally posted by Hedrack:

Lunar visitor is for a secret boss that gives the 4th spell.

Thanks!

I'll go do that. Now I have to wonder what this missing shop achievement could mean if I have bought everything in every square that 'is a shop' according to the map.

Sure, give it a bit, I'll go cobble together my map.

[Shotgun Justice]

My map with 100% exploration: https://ibb.co/dLBncCg

[Demajen]

There'll be an upgrade to the fourth spell to buy. That's what I was missing :)

[Hedrack]

Much appreciated Shotgun Justice! I was able to get 100% map completion and the last health leaf.