Acidic Slime: A utility creature. Useful for blocking because of deathtouch. Can be reanimated with
Reveillark. Can also destroy lands so if your opponent is playing a color intensive deck you might consider destroying the lands in colors they have the least of.
Adarkar Valkyrie: Very useful in the lategame. Can be used to save your own creatures or to steal an opponent's if you use a kill spell on one of their creatures. Since she has vigilance, you can attack and then tap her to save/steal a creature killed during the combat step.
Archfiend of Depravity: Useful creature that shuts down opposing creature-based strategies. Gets around hexproof and indestructible because it forces an opponent to sacrifice. Also attacking for 5 in the air each turn can close out games for you.
Archon of Justice: Another biggish flying creature. This guy is useful for funk-blocking (making a block where both creatures would die but then sacrificing your creature to get value from the sacrifice outlet, like Viscera Seer.)
Avatar of Woe: Can be a little difficult to cast early on, but can greatly control the boardstate once you cast her. Also attacking for 6 with fear as a form of evasion is useful. Just remember she can't attack and activate her ability in the same turn. I rarely get to cast her for her reduced cost but it happens on occasion.
Bloodgift Demon: A source of card advantage and another evasive attacker. Losing 1 life a turn in commander is generally not a big deal, and if killing yourself becomes a risk, you can sacrifice him with any sac outlet.
Crypt Ghast: A form of ramp for black. Can also be used for repeated pinging with the extort ability. Currently there are only 7 swamp types in the deck (shocklands count), but I am hoping to up that number.
Dauntless Escort: A way to protect your creatures from board wipes. This guy is also pretty broken when comboed with Sun Titan.
Deathrite Shaman: A utility creature that is an excellent turn one play. The exiling from his ability is useful against graveyard reliant decks. Make sure to not exile anything you may want to use with Teneb later.
Disciple of Bolas: Another form have card advantage, and the additional lifegain is helpful. The best targets are probably Archon of Justice, Reviellark, and Greenwarden of Murasa. Sacrificing a Terastodon with Reliquary Tower in play would also be pretty sweet.
Elvish Mystic: Simple turn one ramp. Can be sac fodder later on.
Eternal Witness: Adds to the resiliency of the deck, allowing you to get back something that was previously killed. Can also be used to get back spells.
Fiend Hunter: Combos with Sun Titan and a sac outlet for infinite enter the battlefield triggers. It is also a good way to stall opposing threats.
Fleshbag Marauder: An amazing utility creature and one of my favorite creatures to recur with Teneb. I usually target him as the creature I have to sacrifice so he can be brought back from the graveyard later. Reveillark target.
Greenwarden of Murasa: Similarly to Eternal Witness, adds to the deck's resiliency with the added benefit have returing something else upon death. Just remember that if you exile him for his second ability you can't bring him back later.
Juniper Order Ranger
: Provides utility in the form of increasing your creatures' stats. Can also be played before Teneb to start a three turn clock. (If Teneb gets 7 power, he just needs three attacks to kill with 21 commander damage as opposed to the four turns it would take with 6 power.)
Karmic Guide: Allows creatures to be returned from the battlfield. Part of an infinite combo with Reveillark, a creature of power 2 or less, and a sac outlet. Paying the echo cost is not usually necessary unless you need blockers.
Loxodon Hierarch
: Like Dauntless Escort, provides a way for your creatures to survive board wipes. Also pads your life total a little bit.
Magus of the Will: A cheap (monetarily) Yawgmoth's Will on a creature, it allows us to play threats from our graveyard or could be as simple as getting to play Harmonize again.
Mother of Runes: A turn one play, she protects Teneb and your other creatures from targeted removal or she allows them to get through blockers.
Qasali Pridemage: A rattlesnake card (sits on the battlefield waiting for the wrong opponent to step on you) that deters opponents and also gives Teneb 7 power for that three turn clock.
Reclamation Sage: Removal on a creature. Reveillark target.
Reveillark: An evasive attacker that is more commonly used for its ability to bring back creatures from the graveyard. The evoke cost is helpful, but not always necessary. Combos with Karmic Guide.
Sakura-Tribe Elder
: Early game ramp that helps you fix your colors. Can also be recurred to get more lands.
Sepulchral Primordial: A big creature with evasion (Intimidate means it can't be blocked except by artifact creatures or creatures that share a color with it.) Can also use some of your opponents' creatures, increasing in value with the number of opponents.
Solemn Simulacrum: Another form of ramp that also has the added benefit of generating card advantage when it dies, making it an ideal chump blocker.
Sun Titan: A large creature with a nice ability, allowing you to reuse important cards, including enchantments like Aura of Silence.
Terastodon: A large creature and a way to get rid of pesky planeswalkers. It's a shame he doesn't have trample. Can be used similarly to Acidic Slime in order to get rid of an opponent's lands in a specific color.
Thalia, Heretic Cathar: A way to slow down fast, creature-based decks. She is also a good blocker in the early game because of First Strike.
Viscera Seer: Probably the most efficient sac outlet in the deck. Can be played on turn one and enables you to sacrifice creatures in response to targeted removal, which is especially helpful against exile effects, as you can sacrifice the creature, putting in the graveyard so you can use it again.
Yavimaya Elder: Early game color fixing and a source of card advantage. A prime target for recursion effects in the early game.