Best Strat during boss: Get dash and regen and max out relationship, run, jump healing, and fortitude... once maxed out face boss...
Use boulders boss summons to hit boss, collect gems... if you are low on health, dash into the wall and stay still to regen...
5/5 awesome game, just one thing, i've noticed that if a gem has teleported back and the circle is still there, they can come up to the circle and still grab the gem even when its in the cave... is this a glitch or intended?