Any host worth his salt knows that if your guests are hungry, they're not having fun. To combat this, we have to make sure we keep a steady supply of snacks rolling to keep our party running smoothly, and so that we always have access to our best goodies.
Hands-down, our best form of card draw/selection comes from Sylvan Library. Extra cards are amazing, and the loss of life is negligible (But it does add up so don't be too greedy!) Even if you don't draw any extra cards, being able to manipulate your draws and the top 3 cards of your library is still amazing and an almost completely unique effect for green.
Jeska's Will is amazing, especially in a deck that will have its commander out almost 100% of the time. It ramps us and provides much needed card advantage, so it was a no-brainer to slot it in here.
Our best bang-for-your-buck card draw in the deck is from Greater Good. This is repeatable card draw that can net us a ton of cards since our deck mostly consists of huge creatures. It can also be a good way to get value out of a board wipe or removal spell that is targeting one of your big threats, turning them into card draw and potentially making an opponent use some removal. This is an all-star in this deck!
Rishkar's Expertise is similar to greater good (And incidentally an amazing card), but is not repeatable. It allows you to draw cards equal to target creature's power, which in this deck means that you can reliably draw anywhere between 8-40+ cards, depending on how desperate you are. On top of that, Expertise allows you to play one of those cards you just drew for free (As long as its cost is 5 or less), and playing things for free is often good.
Momentous Fall and Life's Legacy also let us exchange a big creature for a bunch of cards. Momentous Fall being an instant also makes it great insurance against removal.
Return of the Wildspeaker is another great draw spell that will give us lots of cards. In a pinch, it can also be a decent buff to our creatures, so it's flexible. Being at instant speed basically seals that this is a strictly better Soul's Majesty.
Garruk's Uprising is a new card from M21, and it is a home-run all star in this deck. It does everything you'd want for a Xenagos deck. Draws you a card for having big creatures? Yup. Gives your big creatures trample? Mhm. Continues to draw you cards for playing big creatures? Heck yeah! for 3 mana, this card is insanely useful at any stage in the game.
Escape to the Wilds is a decent card, providing card advantage and an extra land drop. As far as 5 drops go, it's not the worst.
Neheb, Dreadhorde Champion is an excellent source of filtering away bad cards and producing mana. It gives us new cards, makes mana and hits for good trample damage. One of the best 4 drop beaters we have.
Another great value card for any creature based deck, especially ones with big creatures, is The Great Henge. The best thing about this card is that it fills the role of both a ramp card and a card draw card! I've put it into the draw category simply because there is a chance that you'll be casting this during the mid or late game if you don't have a big enough creature (Even though that's unlikely since the deck is all about huge beaters.)
Elder Gargaroth is a slam dunk in this deck. Not only is it a big body with trample for 5 mana, but with vigilance and Xenagos giving it a power up with haste, you can immediately start taking advantage of its abilities the turn you play it. The fact that it can also trigger when you block is useful, especially to deter attacks from your opponents in fear of you drawing a big threat or developing your board.
Bonders' Enclave is another good way to draw some extra cards along the way when you have some mana left over. Not amazing, but any bit of card draw is welcome in an aggro deck so we can prevent running out of steam.
Dragonborn Champion is another slam dunk for this deck! Turning all of your big creatures into mini draw spells when they make contact is really good, and it's almost a guarantee that every creature we have will be doing at least 5 damage to someone.