There is a way to get spirit light (needed some condition).
Guide to Getting Spirit Light
First, We need skill 'Bash' and four spirit shards on the next image (for fast monster respawn, you must equip 'Turmoil shard').
Next, go to the place of Kwolok's hollow on next image (there is a sprit well nearby, it is so convenient).
Collecting Spirit Light
In ori game mechanism, monsters are die immediately when are killed by environmental trap. Using this, place ori on the position of the image and use skill bash to monster rushing to throw away left side trap
It may seem to inefficient. but the more you kill same monster, the more you get the sprit light from the monster because of synergy of shards ('Bounty' and 'Light Harvest').
Tip: If ori goes to other place or catch other monster, the count is refreshed (use this tip when your computer is lagging).