Chamale said:
Underground Sea is a land that costs 300 dollars. It is a dual land that is certainly better than the basic lands, and this is simply too powerful. It's not broken like Yawgmoth's will, but it's an early example of a land with a ridiculous power level compared to the other things around.
Side note: wherever you buy your cards from, give them the brush off, because they're charging double what Underground Sea is worth (granted, $150 is still a ridiculous price tag). Anyway, I don't really understand your point, it's better than basic lands, so that's bad? Are you saying we should only play with basic lands? Dual lands are the glue that hold multicolor decks together, and without them Magic would be boring as hell. The Alpha duals are finely designed lands (a little on the strong sides), and the only reason they haven't been reprinted is collectors whining about their precious investment losing value.
Treachery is a symbol of every Urza card that let you untap all of the lands used to cast it. It is not a single broken card, but part of a mechanic that was completely broken. With Lotus Vale [http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=4593] it becomes even more absurd.
I will give you that an untap land mechanic, in a set with Tolarian Academy, Gaea's Cradle, and Serra's Sanctum might have been a bit busted.
If you think Wild Mongrel isn't broken, I strongly doubt that you played the game during the Odyssey block. At the time, there was a saying that everyone used the Dog or the Tog. With so many Madness cards running amok, the Wild Mongrel's free discard for a useful effect made it hard to kill, and capable of casting various [http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Basking%20rootwalla] spells [http://gatherer.wizards.com/Pages/Card/Details.aspx?name=fiery%20temper] very [http://gatherer.wizards.com/Pages/Card/Details.aspx?name=circular%20logic] cheaply [http://gatherer.wizards.com/Pages/Card/Details.aspx?name=arrogant%20wurm], as well as filling the graveyard with Flashback effects.
That's not broken. That's synergy, and it's something cards desperately need today. The fact that Wild Mongrel was dominant is far from it being broken. Broken cards win games by themselves. Jace the Mind Sculptor is broken. Wild Mongrel just plays well with other good cards. Perhaps his level of synergy is too high, but it's still preferable because if you have a Wild Mongrel, but they've impaired your ability to pay madness costs, or destroyed your draw engine, all you have is a bear. On the other hand, if they have a JtMS, or a titan, or an Eldrazi, or a Baneslayer angel, you better deal with it, or they win. See the difference? Mongrel is part of a chain in which any link can be attacked to reduce the power of the others, but modern monsters are self-contained victory conditions.
PS: If the options are between the devil who costs $80+ a piece, and the devil who is an uncommon, I'll take the uncommon. At least then everyone can compete at the same level, without worrying about the size of your wallet.