Card of the Week Contest #439: Nom de Sticker

Urza's Ancient Mox
Legendary Artifact
Add . Activate this ability only if you control three or more Urza's lands.
"When over why." - Inscription found on the back of the gemstone

The words I picked were "Cool Fluffy Hydra"

I get what you are trying to do, but there's a serious problem rule-wise regarding your entry:

Normally, X doesn't show up on power/toughness, since most of the time X that's a) on a permanent and b) not a part of the cost is treated as 0, according to rule 107.3g:
Although you can say rule 107.3m can apply here, defining the X toughness constantly:
Yet announcing the {X} cost is either an ETB triggered ability or replacement effect. Based on the existing comprehensive rules, the X is equal to whatever you choose only when the spell is on the stack, and X will lose its value once it hits the board.

Provided, if WOTC actually start print this kind of card, new rules regarding placeholder number X needs to be established, and it can theoretically work. But the reason they didn't do this long ago is the same reason we have counters on cards: On tabletop games, the altering of card texts needs to be as minimal as possible, otherwise it will be confusing. (Isareth is the perfect example where they decide to add decorative corpse counter to remind the players that the reanimated creatures have the additional "unearthed" ability.) As to your current entry, while you can say an additional rule can be written to mandate that it works, unless you needs a dice to determine the value of the X that's a constant nonzero number, other players or even yourself would be likely to forget what X is. (In the scenario where dices or counters are involved, you might as well change the rule so that it puts counters on itself.)

This is different than the indefinite value of (*) on power/toughness, where the value is almost always defined by a certain ability on a card.

Eternal Robot Blood.



note: If was paid, it triggers sacrifice triggered ability but does not dead triggered one.

If I recall, Urza's is a land type. So...

Got myself three random stickers and this is the result:

Familiar Robot Myr
Artifact Creature - Myr Robot
: Add one mana of the color of your eyes.
1/1

Idea: Edited it. How about now?

Problem solved, I reckon!

---

Failed Experiment 
Creature - Phyrexian Elf
Failed Experiment deals damage to creatures in the form of +1/+1 counters and to players in the form of experience counters.
“Wait, this isn’t how this is supposed to work!”
— Tawgmoth

---

My words were: Yawgmoth Pea-Brained Elf

Lady: You need to remove the "When".

spazlaz: you need to remove the apostrophe of "owner's".