Since you're only at 57 cards right now, have you thought about adding 3 Parallel Lives?
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It looks like it would be pretty hard to pull of the Kessig Wolf Run since your only source of green mana is Rootbound Crag, which you only have two of. I would either add some forests at the expense of mountains or save some money and drop the special lands all together.
Have you thought about putting Phylactery Lich in there? It might be kind of hard to get out with a two-colored deck, but it would give you a little more threatening 3-drop to buy time for Worldslayer.
You might want to take out two Hedron Crabs and replace them with Mirror-Sigil Sergeants. Those are your only real way of dealing significant damage, and you have plenty of ways of blocking/ incapacitating enemy creatures. I think it looks pretty good, but it might be a little shy on land (especially if you add more Mirror-Sigil Sergeants).
If you want to ramp up your draw power a little more, you should replace Goliath Sphinx with Consecrated Sphinx. That way you can constantly have card advantage and still get a good flyer out. Also, you should replace Unsummon with Vapor Snag. It's the same thing except that it also deals one damage to the player. If you want a little more control, you could also add some Psychic Barriers.