Combat and Board Presence Many decks emphasize dealing combat damage with well-supported creatures
While Underworld Breach has the downside of giving your cards Escape 3 (and causing you to blow up your graveyard in the meantime), it also has the incredibly relevant effect of not exiling the card that youre casting
Being in mardu also gives you access to Ruinous Ultimatum, one of the best board wipes that can be easily cast with an excess of Treasure for mana
What makes this one interesting is the untap
You can either create a 2/2 Cat Beast token, or you can put a +1/+1 counter on all of your Creatures, and then they all gain vigilance until end of turn
That means that you can very quickly end up with significantly more land than is fair, allowing you to easily make some powerful moves early on (like, say, playing an eight-mana planeswalker on turn four)