Keyword Challenge

{Text}Fuel Can Carrier
Creature - Human Carrier
Whenever one or more fast creatures or vehicles you control deal combat damage to an opponent, put a +1/+1 counter on target creature. This ability triggers only once each turn. (Creatures and vehicles with double strike, first strike, flash and haste are fast.)
1/1

Rush to the Finish Line
Instant
Target creature gets +2/+0 and gains haste until end of turn. If you control another fast creature or vehicle, it also gains first strike until end of turn. (Creatures and vehicles with double strike, first strike, flash and haste are fast.)

Spare Tire
Artifact
: Untap target fast creature or vehicle. (Creatures and vehicles with double strike, first strike, flash and haste are fast.)

Underdressed Cheerleader
Creature - Cat Fan
Fast creature and vehicle spells you cast cost 1 less to cast. (Spells with double strike, first strike, flash and haste are fast.)
2/2

Top Racer
Creature - Human Pilot
Flash
First strike, haste
2/1

Racing Car
Artifact - Vehicle
Racing Car has flash as long as you control a fast creature or vehicle. (Creatures and vehicles with double strike, first strike, flash and haste are fast.)
First strike
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)
3/3

Sports Report Drone
Artifact Creature - Construct
Flying
Whenever one or more fast creatures or vehicles enter the battlefield under your control, draw a card. This ability triggers only once each turn. (Creatures and vehicles with double strike, first strike, flash and haste are fast.)
2/2

Winners’ Podium
Artifact
, : Sacrifice Winners’ Podium: Exile the top three cards from your library. This turn, you may cast fast creature and vehicle spells from among them. (Spells with first strike, flash and haste are fast.)
, , Sacrifice Winners’ Podium: You gain 2 life for each fast creature or vehicle you control.

Extraplanetary Racing Track
Land
: Add .
: Add one mana of any color. Spend this mana only to cast a fast creature or vehicle spell or to activate an ability of a fast creature or vehicle. (Creatures and vehicles with double strike, first strike, flash and haste are fast.)

Slow Death
Sorcery
Destroy all creatures and vehicles that aren’t fast. (Creatures and vehicles with double strike, first strike, flash and haste are fast.)

{Spoiler}The closest card I could find at this cost to what your card does was Hateful Eidolon. Many other approximate examples were one blue and X costs and even then that usually meant every player drawing cards. With minimal set up, this could draw you two cards, and with a full set up it's one mana to draw five cards. Other than that, the mechanic is simple and nice, with a fitting name, but the card is severely undercosted.

{Spoiler}I really like that you took this different approach of using keyword abilities rather than creature types. While there's nothing wrong with going for the standard I do like to see this kind of variety and exploring the possibilities.

I don't have a ton to say about Imitation Technique, Outclass, Odric's Apprentice or Elite's Dismissal, they are simple but solid cards that seem very fairly costed. I like the way they take advantage of your mechanic as well both counting and using the qualitative aspects. I would comment that Imitation Technique could probably use a "until end of turn" in there somewhere, and I love the flavor of Outclass. I also though Odric's Apprentice might be a reference to some other card, but scryfall tells me I'm mistaken.

Talented Pupil and Combat Virtuoso are conceptually similar and just kind of made backwards to each other (one has all abilities and gains stats, the other has stats and gains abilities), and interesting for the same reason, the different ways the keywords in the skillset each interact with an increase in stats being different.

Training Arena gets into some interesting territory as it can't help you build on the skillsket, however it can help maintain it. I might increase the ability cost by though, seeing as the ability is on a land and gives a permanent boost to the creature, but this is a matter that would likely need playtesting to be sure. Speaking of which...

Stensia Feast Hall I don't know what to make of this card's mana cost. At minimum I think this is a Gaea's Anthem, and this might end up giving +5/+5. But then there are other cards that can also really build up which have less ability for your opponent to interact with the buff's conditions than this one such as Call for Unity and Commander's Insignia. Is this too cheap? Too expensive? Just the right price? Probably in heavy need of playtesting.

{Spoiler}I'm not sure of the bundling of werewolf there, as others have pointed out, but I've seen weirder flavor fails. On the other hand, the effect is a really cool necromancer-fitting one, that is flavorful and really captures the cooler aspects of that kind of archetype. I also really like this particular combination since I would personally love to see the undead word keywording for all that kind of bundle.

{Spoiler}I really like some of the things you did with the mechanic. I love the creativity of deciding to expand components of the mechanic which takes full and interesting advantage of the clause of needing to be specific in what elements are bundled, and Fauna Harmonizer referencing the menagerie not by counting but by checking if they have certain keywords is also a really interesting design avenue.

Redcape Rider: Neat choice of image, and I like the effect summoning a companion which happens to build up your menagerie.

Stampede Trumpeter: flexible, can be either used to take advantage of a menagerie of help to build a fuller one. Neat!

Oasis Falconer:As before mentioned, love that it gives itself a companion that builds up the menagerie, checking for scrying is an interesting effect and I love the fact this card expands what can be part of your menagerie.

Fauna Harmonizer: Love the idea of the effect, don't like how cheap this card is. Double strike, lifelink, deathtouch, indestructible, hexproof etc... on all creatures within the menagerie? Even just one or two is a pretty strong effect, but this can really get out of control and reason.

{Spoiler}Seamonsters is a bit specific to Kiora, which in my view is both one of the weaknesses of this mechanic, but also one of its awesome parts, because it really is just that fitting for that character.

Kiora Atua: Really wants to build itself up with first activated ability seeming like more of a failsafe in case you cant' keep seamonsters around. Or maybe it could help with mana? Since the types within the seamonster mechanic seem to generally consist of very expensive creatures, that does seem helpful, and that fact also helps balance her passive ability. I think you could reasonably pull the ultimate down to 6 though.

Whelming Wave: I think this should be worded "Return all nonseamonster creatures to their owner's hands". Aside from that, it's just an adaptation of an existing card.

Armada Kraken: At first glance this seemed really weak for the cost seeing as seamonsters aren't really played en masse, but because it copies itself it does get to a mediocre statline even without any support. Probably would've just made it a rare, don't think it has anything that specular or weird enough to call for Mythic. I wonder if the design was inspired by Armada Worm.

Karin Voda, Arisen Depths: Giant monster go brrrr. In all seriousness, the card looks pretty good even if it's at such a level of expense that commenting on its balance is difficult, and its not doing anything so broken as to need it I think. I do love gargantuan though, it's a really great mechanic in name, flavor and design potential I think.

{Spoiler}I think these are pretty much all solid designs that are simple enough not to leave much to elaborate on, for good and for ill. I think Roaring Reptile is a good reptile lord, if the name is a bit on the nose for the modern naming schemes, and Hostile Mother has a pretty interesting ability especially as it can help to deal with one of the problems with the timmy strategies that some of the types within reptile often have: Playing something big without immediately impacting the board can be almost a wasted turn or potentially cost you the game. This way each big threat you play can deal with something in the opponent's board.

{Spoiler}Aaaah, chess, the classic for bundles like this! Really good idea there!

Doubled Pawn:Solid and flavorful card. Wish you'd made more pawns though, but that's no real criticism, it's just because this idea is cool and I think the baseline "footsoldiers" of a deck built around this would definitely be soldiers.

Fianchetto Knight: Seeing as the last card is a chess situation, I wonder if this and other cards are also more chess terminology. I assume so given En Passant and Promotion are also such terms, though I must confess not being that familiar with them. I would probably avoid flanking in designs, it's a notoriously bad mechanic because of how confusing it turned out to be in practice. It's one of those rare instances were the rest of the card can't really fix it at all.

Queen in Gambit / En Passant: Both good cards, well-designed and seemingly balanced. Not much to say.

Promotion There's a bit of a flavor fail in not requiring a soldier, and I think this card is super undercosted seeing how it can just bring out a 10 mana creature of your choice from your deck. It's a little restricted to a creature of a certain type, but you presumably already built your deck around this. Lastly "merge" is not a term in MTG, as far as I can tell. I assume you mean something akin to mutate, but I'm not sure how the game functions in trying to mutate creatures without mutate into others without mutate, if it can do that.

Zugzwang: Admittedly, at first I thought this card was just not translated, but it seems to be the right term even in English. It's a good spin on Worst Fears, but may need playtesting to see if it's not too easy to cast. Should probably have a self-exiling clause.

{Spoiler}As with vizionarius I like this take of not just using creature types, but going for other possibilities. I like how this mechanic has a really strong and intuitive flavor as well, and the aggressive overall mechanical design (with one exception) reinforces this.

Fuel Can Carrier:Good way to promote a strategy with a white support, and excellent balancing by limiting it to once per turn. Would only change it to maybe be "one of those creatures" rather than any target creature.

Rush to the Finish Line is nice and flexible, while Spare Tire is a neat card for letting you keep up some defenses even while being aggressive, especially by untapping first or double strike creatures which opponents may not want to block due to the one-sided trades. Underdressed Cheerleader also got a chuckle out of me, and is a good card to add to this kind of collection and speed up your casting, though I wonder if at that cost it's good enough for real use in an aggro deck (seeing as the turn after is already in the early midgame, even assuming you didn't miss any landdrops). Top Racer though is just a neat and simple design.

Racing Car is similar to top racer, but the idea of just dropping a flash vehicle and crewing it has a lot of potential defensively, as well as getting out of certain effects. Overall, super neat card.

Sports Report Drone feels a little out of place here among all this fast and aggro designs. Ignoring that though, SRD also seems to be a bit overpriced seeing as the ability can only trigger once per turn anyway.

Winner's Podium I think this card would have been better as just an instant or sorcery with the first effect. The second effect again seems counter-intuitive to the kinds of strategies these designs are going for, nor particularly well combine with the fast mechanic.

Extraplanetary Racing Track Maybe a little too strong seeing how easily aggro could probably take advantage of this far too early. I would add a minor drawback to the second ability that would be acceptable short term but could bite you long-term, like making this make you lose 1 life with the second activation.

Slow Death Neat board wipe, not even sure if it needs to cost as much as it does seeing as these mechanics are more likely to be present in the opponent's board as well than many other similar conditions.

{Spoiler}It was tough decision, but in the end I think I must give this victory to vizionarius . The mechanic was well-thought of, creative in approach and I feel out of all of them was one of the best taken advantage of and explored in the card designs, which themselves were pretty excellent.

The runner up is Flo00 with both good card designs and my favorite of the mechanics.