The magnet of suck is an item magnet. It will pick up items from very far away and even through blocks. There are 3 modes that it can be in. Normal, whitelisted, and blacklisted.
When in a "listed" mode, the magnet of suck will act differently. If it is in whitelist mode, it will only pick up items that are in the list. If it is in blacklist mode, it will not pick up items in it's list. In order to change the mode, simply craft it with bone meal (whitelist) or ink sacks (black list) around in magnet. To add an item to the list, just craft the magnet with that item. To remove an item from the list, craft it with that item again.
Crafting recipe (normal):
|Ender pearl||Redstone dust|
|Iron ingot||Iron ingot|