Do you plan on being competitive? Or is this for playing with your buddies?
If you're not getting competitive with this, looks fun!
Font isn't card
advantage, both players get the extra draws.
Phyrexian Arena would work very well in this deck.
I like Elixir, but (whether you're competitive or not) you should think of life as another resource. You're not losing at 1 life, and if you could play another card in that slot and win the game, you should play it instead. I play this card in Commander for a deck that spills a lot of cards and needs the GY shuffled back in.
Leyline of the Void is a sideboard card, this is
dead if your matchup doesn't use any graveyard shenanigans.
If your planning on getting a bit competitive, you should start netdecking. Once you've played proven successful decks enough, you start to understand why each card is played, and what works and doesn't.
Start here for this deck. PS - this is really good advice, if you're going to get competitive, and play at PTQs and GPs etc. you should start by playing netdecks until you really have a handle on card evaluation in the format, particularly eternal formats.
Font is unplayable, giving both the players the draws is not useful. Even if it was one sided at 4 mana, it's not worth it. At 3 mana,
Phyrexian Arena doesn't see play.
Dark Confidant is the way to go, but with cards like
Cruel Ultimatum, you'll take too much of a hit. Go with things like
Thoughtseize or
Foresee for draw (but be careful about the sorcery timing on the latter, in control you usually want to be saving mana for the right time.) If you play
Snapcaster Mage (which you should, thats a great way to get card advantage)
Forbidden Alchemy can be a great way to go.
Elixir is also unplayable. Life gain on its own is not worth it, like I mentioned above, life is a resource, so use it. Shuffling the GY into the library has anti-synergy with the snapcasters that you just added (
) Lifegain spells that are worth it are ones that are tacked on to otherwise great effects. I play
lightning helix in my American Midrange/Control deck, because it kills a threat and offsets the suicidal hit from fetch/
shock lands. Note that I run the full 4
lightning bolt first,
then fill in the rest of the burn that I need with helix. Bolt is that much better because it costs 1 less, and I can stand to not have the three life if I can win the game.
In competitive magic, especially tight eternal formats, mana cost is VERY important. Bolt gets it done at 1 less mana than helix, so run 4 of those first. You can kill a
Dark Confidant on T2 on the draw, or a
Deathrite Shaman on T1. You can Snapcaster it on T3. Getting things done even a single turn earlier matters, and is the reason we
call these formats 'tight.'
In competitive magic, efficiency matters, even at the same (low) cost, your spells need to do the most possible. Even if
Phyrexian Arena cost 1B, the same as
Dark Confidant, it wouldn't get played since the 2/1 body can be useful, and you need to
squeeze out every marginal advantage that you can.
Extirpate,
Surgical Extraction; choose one, and you don't need 6, this is really just for the big threats. PS- choose
Surgical Extraction, you can cast it for 0 mana, and you're usually exiling big creature threats, or playing it when they don't have the mana to cast a big instant (like sphinx's
revelation) anyway. Side in
Extirpate for control matchups if you really need to be removing instants.
Add in some counters in the slots for these cards you're taking out.
Mana Leak or
Rune Snag are Modern Favorites. A
dispel or two might be nice to
protect your big threats (
Cruel Ultimatum) from counters.
Spell Snare is great in the format since people play so many 2 mana threats.
Overall, the deck looks fun, and could be a great Grixis Control Deck. Consider
Aetherling as a finisher as well, just make sure you always leave up mana to
protect it. And read the Cruel Control Primer I linked to above, there's so much more good advice in it.