Lumbering Falls
Oracle Text
Lumbering Falls enters the battlefield tapped.
: Add or .
: Lumbering Falls becomes a 3/3 green and blue Elemental creature with hexproof until end of turn. It's still a land.
Card Rulings
8/25/2015 A land that becomes a creature may be affected by “summoning sickness.” You can’t attack with it or use any of its abilities (including its mana abilities) unless it began your most recent turn on the battlefield under your control. Note that summoning sickness cares about when that permanent came under your control, not when it became a creature nor when it entered the battlefield.
8/25/2015 This land is colorless until the last ability gives it colors.
8/25/2015 When a land becomes a creature, that doesn’t count as having a creature enter the battlefield. The permanent was already on the battlefield; it only changed its types. Abilities that trigger whenever a creature enters the battlefield won’t trigger.
8/25/2015 An ability that turns a land into a creature also sets that creature’s power and toughness. If the land was already a creature (for example, if it was the target of a spell with awaken), this will overwrite the previous effect that set its power and toughness. Effects that modify its power or toughness will continue to apply no matter when they started to take effect. The same is true for counters that change its power or toughness (such as +1/+1 counters) and effects that switch its power and toughness. For example, if Lumbering Falls has been made a 0/0 creature with three +1/+1 counters on it, activating its last ability will turn it into a 6/6 creature that’s still a land.
I do kind of wish it ALWAYS had Hexproof though, as opposed to just in creature form. It might not matter much for standard, but in Modern et. al. it's not as impressive as it'll likely just be "I respond to your activation on the stack with Tec Edge/Ghost Quarter activation targeting it." If it just always had Hexproof it would have been more interesting as then it also helps fuel some of the green devotion strategies that rely on enchanting lands to ramp more safely.