Valky
Arcane

From some gameplay videos I saw of the initial gameplay demo a while ago, the metroidvania aspect of it (2D platforming/exploration) seems underdeveloped and extremely barebones, with very little in the environment and just a treasure chest put here and there otherwise being long corridors between different monster fights and destinations. Where all of the development however does seem to be going into is the turn based combat and monster stats/collection aspect. Every monster has unique skill trees and plays differently, and aside from possible balance concerns the combat contains a fair amount of depth.https://monster-sanctuary.com/This looks like a pretty neat idea.
https://www.kickstarter.com/projects/1286599243/monster-sanctuary-monster-taming-metroidvania
edit: Free demo https://sersch.itch.io/monster-sanctuary
The gameplay concept is really cool, 2D exploration style game with creature catching/collection that adds to your party with unique skill trees and turn based battles.
I wonder when final release will be? I'll totally play this. Years ago I remember seeing this campaign.
The closest I've seen to this is Monster Tale on DS. As a concept, it certainly has a lot of potential. But developing such a thing sounds like a nightmare. Not only the pseudo-freedom of a metroidvania map, but also the freedom of customizing your team of monsters. I'm imagining using unique monster abilities to progress in more than one way.