If a card with dredge N is in your graveyard, any time you would draw a card, you can instead mill exactly N cards and put the card with dredge into your hand
Arcanis the Omnipotent Speaking of Onslaught and powerful Wizards, how does Omnipotence sound
This could be made more appealing with various tweaks, lower the energy cost on coloured mana to one, remove lift cost on coloured mana etc
Having your opponent lose three life if it's a legendary creature is a neat bonus, but not as great as everything else Ringwraiths can do
Conspicuous Snoop made me hopeful for Goblins in Historic and gave us some great new combos to work with in Modern
Every time your goblins attack, you get more goblins, and every creature that enters your side of the field pings your opponents