Previously in one of my maps (Deadly Hate) I added essences as a way to pick up lesser items to add stats that could stack, until lets say you get a plus 5+ INT essence. I reworked that idea into something more melee/like friendly. Shards of power are a LVL1 item you can stack, you can only carry one of them and get their max effect once per hero.
They add a +1 to either STR, AGI or INT, after 3 stacks it grants + 2 and at 6 stacks it grants plus 3, at 10 stacks the item can be consumed with a magic gem to infuse your hero permanently with +3 to the choosen stat plus the gem effect (lets say +3% all damage). Collecting Shards and gaining levels while the hero wears one allows you to increase the stack level on your Shard of Power.