Mind Twist is a card that can be used to make your opponent discard their hand
In a mono-blue setting, where mill tactics are traditionally strong, Bruvac accelerates this win condition dramatically
In order to play any of these (and there are some worth playing), you'll really want to be able to wrap your arms around the spell-side
In Magic terms, its a twist on the adventure mechanic that allows you to cast permanent spells from your hand for a reduced cost
There is a way to template the ability so that it technically reads a little more blue (for example, instead of preventing the casting, it could allow it and then counter it) but it would just have been significantly wordier and would have had the same basic effect
Speaking of unique equipment, a Sword that can cause someone to lose the game on the spot more than qualifies