I maindeck a Sword of Light and Shadow in my Bant deck .
If you put it on a 2+ thoughtness creature it makes it Stp, Abrupt Decay and Bolt proof.

Additionally against Miracle and DnT, every creature becomes a True-Name Nemesis
it lets you recover a little life up and overall allows you to recover your Snapcaster Mage which can be used as well, at that point, as blocking walls + flashback each turn for freaking huge card advantage on Stp and Brainstorms.

I side 1 Sword of Fire and Ice for the Grixis/UR matchup and I normally save my StP for Angler and Tarmogoyf or whatever will not trade with my creatures.