albytheracistdragon

I'd say if you use Voyage's End for +1/+1 counters, sideboard Lost in a Labyrinth and bring it in for decks without them.

But the ability comes after combat, so casting the extra card could be potentially a waste.

Use Hidden Strings maybe? Untap the Starfish and Flamespeaker so you can pump the Flamespeaker into a sizeable blocker.

Oh I suggested the scry 2 just because it helps more than scry 1, not necessarily to boost flamespeaker extra with the 2. But a lot of people don't realize that I've noticed

Well, if you're looking for cards to cascade into, you could use Pulling Teeth, Blightning, Coercion, Flame Javelin, Skullscorch, Smallpox, Stupor, Despise, or maybe even just Mind Rot. Or, if you want to use Sarkhan with it, you could use Pain Magnification.
If you want larger cost cards in the more 4/5-mana area, you could use Rise//Fall, which has a converted cost of 4, but only costs (R)(B) to cast the side you want. Also Mental Agony,Persecute, Reforge the Soul, Void, Cone of Flame, Explosive Revelation, Poison the Well, Pyrokinesis, Rekindled Flame(if you combo it with discard), Riddle of Lightning, Hit//Run, Runeflare Trap, Shriveling Rot, or Soul Spike.

I wouldn't recommend all of them, most might not fit what you had in mind, but the high cost CMC cards you can cast for alternate costs and the fuse cards would get passed up by cascade but also be able to be cast when they make it into your hand.

Well, if you're looking for cards to cascade into, you could use Pulling Teeth, Blightning, Coercion, Flame Javelin, Skullscorch, Smallpox, Stupor, Despise, or maybe even just Mind Rot. Or, if you want to use Sarkhan with it, you could use Pain Magnification.
If you want larger cost cards in the more 4/5-mana area, you could use Rise//Fall, which has a converted cost of 4, but only costs (R)(B) to cast the side you want. Also Mental Agony,Persecute, Reforge the Soul, Void, Cone of Flame, Explosive Revelation, Poison the Well, Pyrokinesis, Rekindled Flame(if you combo it with discard), Riddle of Lightning, Hit//Run, Runeflare Trap, Shriveling Rot, or Soul Spike.

I wouldn't recommend all of them, most might not fit what you had in mind, but the high cost CMC cards you can cast for alternate costs and the fuse cards would get passed up by cascade but also be able to be cast when they make it into your hand.

Yes, I see the cascade, but I think the amount is a little too high, and you're likely to draw into them very often early game.

The plan is foolproof if they don't have any counter spells, so I'd say I'm fairly impressed with an idea I used to scoff at.

I'm a little concerned that most of the deck is too expensive for what you're trying to do. But I like the idea here. Maybe make a dead-planeswalker duel deck, with Vensser as his opponent

Hmmmm sideboard maybe?

Well, in defense, having that untapped land is usually better, but at the cost of having to deal with getting the right lands. Should be fine.

I always saw potential in flamespeaker, but usually in draft. I'd say sideboard some Mizzium Skins to protect your creatures and maybe a few of the usual sideboard cards, ie Ratchet Bomb and Pithing Needle, but perhaps even try using one of the Fated spells for their scry 2.

It most certainly is not! I think out would be fun to include the creature Nicol Bolas, as they can both be played at the same time (?)

Well, going along with the viking theme, you could use cards like Scab-Clan Mauler, Rip-Clan Crasher, Kruin Striker, Skarrgan Pit-Skulk, Keldon Marauders, or even Beastbreaker of Bala Ged to change things up. Some of these might be outclassed though, so I'd mainly look into Beastbreaker and Kruin Striker, see how they work out. Could become a decent tribal.

Well and anything he does for you can help just about any deck that can play him in. I've actually seen quite a few very competitive RUG decks with him and Kruphix as the MVPs

Use an arcbound creature base! That or make it R/U to use Izzet stuff.

I'm sure you could find something other than prophetic prism, honestly. Or perhaps substitute it for another good control card, like Izzet Charm. Believe me, it's pretty good in tight situations.

How does this deck hold up against other modern decks? Seems fairly aggressive, but almost midrange. Also, I think Burning-tree would thrive here, seeing as you could play literally half of the cards here with that extra 2 mana

Usually when I see her played, there's a clever plan or a noob involved...

as long as you gain a little life with courser and keep the pressure on with mistcutters and savageborns, you should be fine early game. Also, nykthos and elvish mystics are one of your best bets to speed up your deck, as well as jack up your hydras to be huge. Personally, I got my ass handed to me recently by a very similar deck that used domri rade and burning-tree emissaries for devotion/mana to activate nykthos.