this is tough 'cause it's a very holistic thing: most obvious would be to make an X spell that caps out, but that's pretty similar to a round we already did, so let's go with make a creature with in its mana cost that doesn't have the endless one ability. just, like, do something else with it. anything else. preferably something interesting, but hey, I'm not your boss, do what you want.

grading on Friday as always. go!

Kroesh, Slumbering Wrath
Legendary Creature - Eldrazi Golem (M)
When Kroesh enters, create X Powerstone tokens.
Kroesh enters with a dormant counter. (Creatures with dormant counters can't attack or block.)
Trample
: Remove a dormant counter from Kroesh.
10/10
It loomed over the horizon, a slumbering mountain of violent potential waiting silently for its masters return.

in the interest of fairness, I should note that the criteria specifies the X is in the creature's mana cost.

ty good sir.

Does this qualify, or is Sunburst on an X too similar to Endless One?

Bringer of All Twilights

Artifact Creature - Phyrexian Bringer
Sunburst
Remove a +1/+1 counter from Bringer of All Twilights: Choose a color that hasn't been chosen, then exile target permanent if it is that color.
0/0

Spirit-inviting Medium

Creature - Human Cleric
Delve
Spirit-inviting Medium has all abilities of creature cards exiled with its Delve ability.
"The priestess seemed quite unassuming, so that we thought we were dealing with a novitiate at best. Iori remarked on it, and quite rudely. Then we saw the shadows, and knew what kind of thing we were truly in the presence of." - Soren Eastwind, On The Gods and Specters of the Outer Isles.
0/1

Update: Made it red/green hybrid because both colors care about lands AND they both can achieve casting it in different ways. Red can use temporary mana (like Seething Song to cast it on T3). Green can use mana dorks (like Llanowar Elves to cast it on T3).

I'm torn but I know in judging I'm gonna be like "dunno if this counts" so I'm just gonna say it doesn't. the real point is to do something other than "this creature gets bigger if you spend more mana" and I don't think sunburst is far enough away from that.

Omenpath Ooze
Creature - Ooze (R)
When you cast ~, copy it X times.
When ~ enters, you may exile any number of spells you control. If you do, put two +1/+1 counters on ~ for each spell exiled this way.
All roads lead to doom.
[2/2]

multiple Xs is fine.

Zenith Primordial
Creature - Avatar (M)
Progeny X (When this creature enters, create X token copies of this creature, except they’re 2/2 creatures without progeny.)
First strike
When this creature enters, exile the top two cards of your library. For as long as you control a creature named Zenith Primordial, you may play those cards.
6/4

I came up with a nifty X spell yesterday and I was hoping today's contest would let me post it but it's not a creature rip

just stick it to a creature body and call it a day

My first try is just gonna ignore the contest requirement and make a creature that becomes bigger for each x you pay.

Herald of Hopelessness
Creature - Horror Cleric
This creature enters with x insignificance counters.
Creatures your opponent controls get -1/-1 for each insignificance counter on this creature.
"It's the smallest, most pathetic horror you could even imagine, and that is what drives the point home"
0/1

And they just spoiled Mockingbird.
#SartarasWas1st

Runewing Artisan
Creature - Human Artificer (R)
Runewing Artisan enters the battlefield with X flying counters on it.
At the beginning of combat on your turn, you may exchange a counter on Runewing Artisan with a counter on another target creature you control.
The runesmiths of Varran share designs freely, each one eager to see the art reach its highest form.
2/1

Siege Master
Creature - Human Knight (R)
First Strike
When this creature enters the battlefield, put a siege counter on up to X target permanents.
: Exile target permanent with a siege counter on it.
Where artillery can't open the gate, starvation can.
2/2

Mazeura's Torment
Creature — Snake Nightmare Horror (R)
When Mazeura's Torment enters, choose X cards in your hand and exile the rest.
When Mazeura's Torment leaves the battlefield, put the exiled cards in their owners' graveyards.
Chainer's name from his days as a nobody boy from a nowhere village is only known by the Patriarch and the things winding and hissing in his dreams.
7/5

Autotomimic |
Creature - Shapeshifter

You may have ~ enter as a copy of any creature or artifact on the battlefield. If you do, remove X counters from it and/or that permanent as it enters.

0/0

Kinda dancing around the prompt here, but:

Wisdom —
Creature — Incarnation (R)
When Wisdom enters, draw X cards.
Wisdom's power and toughness are each equal to the number of cards in your hand.
“Advice is a two-way road,” Multani sighed. “I can tell you what I think you need to hear, but you also have to be willing to hear it.”
*/*

Omnath, Newborn Locus
Legendary Creature - Elemental (R)
When Omnath, Newborn Locus enters the battlefield, add X mana of any one color.
You don't lose unspent mana produced by creatures as turns and phases end.
The song of creation, the voices of all.
1/1