My primary world, home of the original Glass Island and Skyrail system.
My modded world, featuring the delightful 
Super Hostile - 
With great trepidation I returned to the Shadowheart, visions of the mob army still fresh in my memory. What did I know about spawners... well, they don't spawn mobs on lit blocks. So my best defense would be the sun - lighting up the dark heart of this tree to tame the beasts within.
Carefully removing one block at a time, glass replaced wood, to light the spawner pit when the sun would rise. That'd take care of the skeletons, but not the creepers... hopefully my shelf pine base was far enough away that they'd despawn.
Could my plan have worked? The core was empty of mobs, nothing but fallen wood blocks from yesterday's roof making. Slowly inching my way down, I poked at the shiny silver blocks. Iron! Well that's a welcome addition to my supplies. Hastily grabbing the fallen logs, I spot two large holes at the bottom of the trunk.
That won't do, but it explains how the mobs were getting out of the spawner area earlier. A few wooden planks quickly block off any potential visitors. With one final look inside a spawner, I hightail it back up a ladder and block off the core. This place gives me the creeps, literally.
