Commander
Strategy
This Xenagos, God of Revels is all about combat phases and attacking with massive trample creatures. I've had many interesting games with the current deck list, and hope you get some new deck building ideas.
Early Game
Overall in MTG and in Commander, your play group heavily determines the optimal starting hand for the game. In my play group most of the decks are relatively slow, eg. Jodah, Archmage Eternal Big Spells, Atraxa, Praetors' Voice Super friends. There are some exceptions like The First Sliver Sliver Tribal or Greven, Predator Captain Sacrifice deck. As my play group is relatively slow I choose my starting hand to have minimum of 4 mana available on the start of turn 3. This could be for example 2 Forests and a Sol Ring or 3 Forests and Llanowar Elves.
If the pod has strong interaction or control decks like Brago, King Eternal I play a bit slower, and leave my manas open even if I don't have anything useful to cast to put mental pressure for the other decks and to hinder my own board state to avoid being the #1 enemy.
Mid Game
With mid game I refer to turns 3 to 5. In these turns it is vital to get Xenagos, God of Revels on the table as an enchantment and to provide haste for your big mana ramps like Savage Ventmaw, Selvala, Heart of the Wilds or Alena, Kessig Trapper. Each of these cards give you a massive mana boost an let you to play the biggest spells this deck has.
Usually in mid game you are starting to run out of cards in hand, depending on the tempo of the game. This is a common issue with all aggro decks and this decks tries to avoid running out of cards with creature related draws like The Great Henge, Garruk's Uprising or, Selvala, Heart of the Wilds (multi tasking!).
As Gruul colors have relatively few creature interaction we are focusing on some synergy removals like Ram Through, Purphoros's Intervention and Soul's Fire. All of these are built-in one-off player removals, too. I remember once pumping Purphoros's Intervention to 30/16 trample Elemental token and finishing of a emerging Atraxa deck on maybe turn 5.
As the deck has very straight forward strategy, remove one player at a time, otherwise you'll run out of resources. Trust me, I have made this mistake a few time due to dumb political choices and ended up having 2 players targeting my big beasts.
Late Game
As the game goes further your chances of winning gets slimmer since the amount of interaction is low in the deck. Your big mana is based on creatures so wipes are lethal to your progress so aim to keep the game as short as possible and focus on removing a single player at a time.
In the late game your ultimately best strategy is to exploit multiple combats + Xenagos's boosting. Any of the big hitters like Malignus, Ghalta, Primal Hunger or Pathbreaker Ibex is enough to wipe the whole table in a few combat phases.
Overall review
Who is this for
If you are looking for straightforward, creature based, quite fast decks this deck is for you. Especially if you enjoy seeing the elf-tribal deck putting 10+ 1/1 against your Malignus this deck gives you great times.
Maybe not for you
If you want your commander games to be long (10+) turns and you want to win with Solitaire-like tactics this is not the deck for you in Gruul. Interesting solitaire-like control gruul deck can be achieved with Klothys, God of Destiny.
Power level
7/10
This specific Xenagos deck has power level of 7/10. It can reliably remove 2 players before turn 6 with an okay start in a single turn, but the current mana base is not at all optimal. With upgrading the few 2 and 3 cmc mana dorks to 1-drops you can easily push this to power level 8.
To make this a lvl 9 or better, I would consider cards like Strionic Resonator, Lithoform Engine, Aggravated Assault, Kenrith's Transformation, Song of the Dryads, Balefire Dragon, Combat Celebrant, Prowling Serpopard, Savage Beating, Berserk, Relentless Assault, World at War and Triumph of the Hordes.
Maybeboard
If your opponents have strong tax-decks consider adding more interaction cards and sacrifice card-draw, like Greater Good or Momentous Fall to benefit from losing creatures. If you are facing lots of spell slinging decks focus on putting creatures on the battlefield with spells like See the Unwritten and spells with cards like Ruric Thar, the Unbowed or Cindervines
