7 LS, one off with Wayward Wanderer, 2 with SoG/NJ, one with Burial, leaving 3. Your opponent will be unable to win without SoG/NJ, and if you get Judas' Plot up after they AotL but before they SoG/NJ, they're locked. They're also locked if you snipe SoG or NJ (easy to do if you dedicate a defense to it), if you let them rescue 2 and then activate Altar of Ahaz, if they're not running N.T. Females or the FbtN LS (or you neutralize that soul), or if you Discard a soul by some other means (harder than the rest, but not too terribly difficult to set up with Jephthah or that Demon guy).
There are workarounds through the lock, but this card would make The Amalekite's Slave a staple (fewer staples is a good thing), and make JT almost a staple (since the Hopper can be sniped with Harvest Time or Woman at the Well). The other ways around this lock are useless against any other type of deck, and any strategy whose counters are only useful against that particular strategy is broken.
Another one of the problems is that it takes very few cards to work and can be splashed into almost any deck to make it much better (this was a big problem with TGT). Of the cards needed to make the lock viable, SoG, NJ, Burial, and the restrictive LS's are already in almost every deck, so a player would only need to add WW and a way to play Confusion to any deck and it'd be much better. And since WW is Brown, a Brown or Brown/PG defense with Manasseh would have an easy time of picking off SoG without sacrificing any normal defense in case the lock doesn't work.
Even without the lock strategy, just splashing WW into any deck would create a soul drought, letting you stall. This would be a bad thing as speed would have even more guns in its arsenal, and many speed decks splash Haman's Plot and Gibeonite Trickery anyway. Restricting it to 63 cards or larger would solve both the problem of speed splashability and easy soul lock.
