To be fair, the topic title is somewhat misleading.
There IS treachery in Sea of Blood. However, from what I've seen (from the online rules and glancing at the Avatar sheets that have been posted, which admittedly isn't all of them), it might as well not be.
In regular Road to Legend, the ONLY reason to get Treachery is for Lieutenant fights. In the dungeons, it is next to worthless. That is because good heroes will spend most of the game blitzing only the first dungeon level and then leaving. They will only do more floors once they can do two floors in the same number of turns it previously took them to do one. What's more, good heroes will always prioritize getting Wind Pact, which can drop you shiny new Treachery card if it's in your opening hand for the level. In general, the Heroes are probably giving you about 4-5 turns in a dungeon. That means a 3 card initial hand, plus 8-10 cards. However, it gets worse. Your last turn or two will probably be futile, since the Heroes will have killed all the monsters and are just maintaining an anti-spawn position while they collect the treasure and leave the level. There are VERY few treachery cards (or cards of any sort) that help you in this situation. So really, you will only draw 4-6 cards that will be useful. So let's say you get 9 cards - with all the expansions, your deck is 48 cards. That's less than 1/5th of the deck. And, as I said, good Heroes will have Wind Pact, so if your shiny card is in your opening 3 cards, you won't get to use it either. So it's actually only if you draw it in the first 6 cards that it will be useful - that's 1/8. AND you need to actually have the threat to play it, and a situation to play it in.
So...10 or 15 or 20 conquest for a single card that I'll only even SEE once out of every 8 dungeon levels, let alone actually play? Let's be generous and say that you have an amazing Treachery card that gives you a guaranteed 3-CT Hero kill every time you play it and this card costs 0 threat (note: if you find this card, let me know). If you paid 15-CT for the Treachery to get it, that means it will take 40 DUNGEONS just for it to pay back its cost and break even. No thanks.
Of course, in RtL, it all worked out, because Treachery is absolutely crucial to the lieutenant fights. Actually using it in dungeons from time to time was just a (very) marginal bonus.
From what I can see, Sea of Blood changes this in two ways:
1) No more treachery in Lieutenant fights. And from what I can see, no other place to use treachery other than dungeons.
2) The 2 Avatars that I've seen have MORE expensive treachery than the ones in original RtL!! They pay 15-15-20, depending on color, without having a 'cheap' 10-suit.
So treachery got 10 times worse and MORE expensive? It's sad, because the treachery cards are cool and a fun part of the game, but no Overlord with any modicum of skill should ever buy it under those circumstances.