Grab your Urza's lands and your deck will have the huge mana it needs to cast a Karn
If, during your declare attackers step, Ursine Monstrosity is tapped, is affected by a spell or ability that says it can't attack, or hasn't been under your control continuously since your turn began (and doesn't have haste), then it doesn't attack
Typically, the newer cards dont tend to be worth much, since they are easily found on the market, making it simple for collectors to find cards to complete their set
That means that Tamiyos Safekeeping is pretty much right up your alley
The basic idea of the Sky Striker strategy is using one main monster, Sky Striker Ace Raye, that can change into many different forms
Underground Sea, for example, can sell for as much as the cheapest Power Nine card