Be warned that card prices fluctuate and these will not remain the same forever
Nasty End is your classic sacrifice a creature to draw two cards Black instant, but if that creature is a legendary one, you draw three instead, which is both a great representation of Sarumans end in the books, and a powerful new draw spell for Commander
There is no restriction on the number of legendary creatures you can have in a deck
The key advantage is combining removal, sacrifice, and commander damage in a single threat
This will allow you to easily retreat Toxicroak when it has sustained damage
Early turns generate cards from cheap spells opponents cant afford to tax, while equipment and pump effects follow, increasing the tax rate to prohibitive levels