Commander
Deck list
You can view the decklist in Archidekt here
About Felisa, Fang of Silverquill
Felisas triggers are focused on creating 2/1 flyers when nontoken creatures with counters (any kind of counter!) dies. Felisa also provides a way to give counters to other creatures with the mentor-ability. As Felisa has flying and 3-power Felisa is able to give counters to any creature with power 2 or less relatively safely.
Felisa, Fang of Silverquill in EDHREC
Felisa, Fang of Silverquill has relatively high amount of decks in EDHrec, with close to 1400 decks. Counters and aristocrats themes are both extremely popular archetypes so the combination has very interesting possibilities but lacks the strongest counters color, green. I'd guess, if Felisa would have been in Abzan colors, it would be one of the most popular commanders ever printed!
Possible themes for Felisa, Fang of Silverquill
Counters theme
Felisa's death triggers demand counters to have any impact on the battlefield. But luckily it triggers from every kind of counter, so Felisa works with any kind of counters, not just the usual +1/+1 counters.
Great counter cards: Ao, the Dawn Sky, Archangel of Thune, Bloodtracker, Breena, the Demagogue, Drana, Liberator of Malakir, Luminous Broodmoth
Aristocrats theme
Half of Felisa's token creation triggers comes from death triggers, so having sac outlets and sacrificiable non-token creatures is important. This makes aristocrats theme a very viable and powerful strategy, combined with the counters.
Great aristocrats cards: Blood Artist, Zulaport Cutthroat, Cruel Celebrant, Elas il-Kor, Sadistic Pilgrim
Tokens theme
Whenever a nontoken creature with counters on it dies, Felisa creates 2/1 Inkling tokens with flying. Tokens are the main combat focused wincon with this deck.
Great token cards: Anointed Procession, Basri's Lieutenant, Felidar Retreat, Elenda, the Dusk Rose
Modular theme
Modular is a triggered ability on some artifact creatures. The creatures enters the battlefield with +1/+1 counters, and the modular ability triggers, when the creature dies. The ability allows the controller to move every counter on the dies creature on another artifact creature.
Modular is interesting keyword ability, focused mostly in colorless and in boros colors. Felisa might work as an interesting modular commander, as there are 16 creatures with modular in Orzhov of which 11 are worth of playing, like Arcbound Stinger.
Strategy
The main strategy of counter aristocrats is simple: get nontoken creatures out with counters, get Felisa on the battlefield, and wait for death death triggers while building your engine.
The biggest threats against our strategies are aggro decks as aristocrat decks always demand a moderate or high amount of setting up the board state, before presenting a threat. After surviving the early game and the ramping contest, our aristocrat engine starts to out value other decks (even the simic decks!) with pieces like Grim Haruspex, Midnight Reaper and Morbid Opportunist.
After the aggro decks, the greatest threat are counter-hate cards, like Vorinclex, Monstrous Raider and pinger decks, as many of our creatures have toughness of 1 or 2 in the beginning, making them weak against reoccurring ping damage. Zulaport Cutthroat and Blood Artist are great targets for pingers, for example.
Early game and mulligans
T1 to T3 is the early game. Whole early game focuses on ramping and setting up the counter synergies. Also Orzhov has access to the best removal in the game, so don't be afraid of playing with zero creatures on the battlefield. Part of the strategy is to cast a wrath, resetting the board state, but because of Felisa, this is actually a wincon!
Mulligans: 3 mana sources is the minimum I can recommend, but 4 is the optimum. The deck has many ways to draw cards after having nontokens on the battlefield.
Great cards to play in early game: Any of the mana rocks, Esper Sentinel, Anafenza, Kin-Tree Spirit, Noble Heritage, Lae'zel, Vlaakith's Champion, Luminarch Aspirant, Grateful Apparition.
Mid game
T3 to T6 is the mid game. In the mid game, we focus on getting Felisa out, putting counters on our nontoken creatures and having the aristocrat engine running.
In mid game, the aggro decks have used most of their resources, we have enough mana to cast Felisa, and either have counters on nontoken creatures already, or a way of putting those on our creatures at will. Felidar Retreat and Cathars's Crusade are great for this, as they are likely to avoid most of the removals opponents are running (since only white and green can actually remove enchantments reliably!)
As Felisa has a CMC of 4 and Orzhov has relatively bad ramping, the commander tax is back breaking for our deck. Due to this, avoid casting Felisa as the first creature, since she does absolutely nothing on her own, and is a free target for the opponents.
Great cards to play in mid game: Together Forever, Felidar Retreat, Resourceful Defence, The Ozolith, Mikaeus, the Lunarch, Fain the Broker.
Late game
After T6 is the late game. As our deck is slow, the late game is our territory. The aristocrat engine is running with creatures like Blood Artist or Zulaport Cutthroat. Card advantage is on par with the simic decks due to creatures like Grim Haruspex, Midnight Reaper and Morbid Opportunist.
Most likely the opponents have already noticed how ineffective it is to kill our creatures with counters, as the 2/1 tokens with flying are extremely dangerous. Also the traditional board wipes are dangerous to cast for opponents, as most likely we have Felisa out,
Great cards to play in mid game: Stonecoil Serpent, Cathars' Crusade, Unbreakable Formation, Luminous Broodmother, Ao, the Dawn Sky, Sun Titan.
Winning the game
As with every aristocrat deck, the win comes from a single exploding turn. Often the exploding turn is ignited from an opponents board wipe or as a response from our sacoutlet, practically wiping our own board and draining our opponents, while giving life and draw triggers to ourselves.
Some of the wincons: Blood Artist, Zulaport Cutthroat, Cathars' Crusade, Oona's Blackguard, Felidar Retreat.
Who is the deck for
If you are interested in a slower, aristocrat like deck with a few extra hoops to jump through, and having strong, combat focused win cons, too, I can recommend this deck.
As always, keeping track of every trigger, especially the counter related triggers, demands a lot of concentration from the player. If you are after more straight forwards strategies, or more aggressive decks I'd recommend some other commanders, like Xenagos, God of Revels, or Karlov of the Ghost Council.