This is a great card draw tool, as mentioned below, I don’t think I have to convince anyone about it. But about the deck-thinning aspect, different from what others said, 3x Daeron's Runes make your deck size effectively 44, not 47. If you imagine you only have 2 cards left in the deck, after you play it you have 0 cards, so two cards less than the nominal number (it doesn't matter that you have to discard one, it's as if it never existed in your deck). In terms of card draw, you end up having the same hand size, but you see two new cards; often you have duplicates or cards you are not particularly interested in (or which you give less value to what you could potentially draw), so in many cases you thin your deck by one card (replacing Daeron's Runes) and get a new, potentially interesting card (thinning your deck by one more). A 0-cost card that does card draw and deck thinning this way must be one of the most powerful cards of this type.