the "thing" where you combine soul shards and it adds up kills. For example you go to the twilight forest get a bunch of spawners in a hollow hill. you eat the spawners with a soul shard and have maybe 400 kills on a zombie shard and 600 on a skellie shard. you combine them in an anvil and get a tier 5 skellie shard out of the anvil. the anvil adds the kills to the first shard placed inside no matter the mob in the second. it's exploited further when people take a nuisance shard from say a mineshaft, full of consumed spider spawners and use it in an anvile with a witch chard with 1 kill and instantly have a tier 5 witch spawner.
I like it personally. you still have to find the spawners. But its a moot point since the author hasn't been heard from other than RichardG saying "he's busy" on the Reddit