Senseis Divining Top lets you draw the tutored card immediately, while Necropotence turns that precision into raw inevitability
Spell wise, that means you're looking at having 3-4 mana open for this card, and creature wise, it means you have to have something die on your or your opponent's side
The creative possibilities within those boundaries are genuinely wide open
While I personally wouldnt say this is one of the top five blue cards in Modern, it has been a solid addition to Grixis Shadow as it can combo with Deaths Shadow to create a 13/13 creature for a turn irrespective of your life total, as well as being a solid addition to sideboards of many blue decks in the format
The abilities in question are putting a +1/+1 counter on a creature and giving them First Strike until the end of the turn, creating a 2/2 token with Vigilance, and the ability to exile a tapped creature and gain two life
Giving yourself and your team protection from creatures lets you win the game very quickly by slipping through opposing defenses while protecting yourself from a counterattack