Let's try a few things.

In some of the tries below I didn't realise the URL is unique to a card. In
others, I did, but I copied the URL too soon and it points to an earlier card.

First, some random generation, without "Advanced Options"

Curse of Cripling Memory
[Image: Maybe a laboratory? Someone with his face fading in a dark cloud?]
1U
Instant
Choose a Creature type. You may cast creature spells as though they had flash.
(The blades of the unskilled never rust)

Cloud Portal
3
[Image: clouds, something that could be a flat-top pagoda, maybe runes on the
clouds?]
Artifact
3, {T}: Draw a card.
(Even a whisper can still be heard above the rest of the world.

Note that the {T}ap symbol on this is...red. Like a red mana symbol.

https://www.urzas.ai/cards/?card_id=78e7e720-c965-45f8-82ca-...

Dusk Hovergard
2U
[Image:A blob with a blob next to it]
Creature - Spirit
Flying
When Dusk Hovergard enters the battlefield target creature can't block this turn
1/1
(Can't read the flavour text because the card text is white on white background)

https://www.urzas.ai/cards/?card_id=1ff17f7e-c112-4a58-8ebe-...

Morbid Regimen
2{B}
Enchantment - Aura
Enchant creature
Enchanted creature gets +2/+2
(Once each night, the sleeper awoke to find his house had been transformed into
a death garden.)

https://www.urzas.ai/cards/?card_id=12ce1065-cfa5-4e67-bbeb-...

The following were made with "Advanced options": name, mana cost and type chosen
by me.

Booby Trap
2B
[Image: something steampunk?]
Enchantment
Whenever a creature attacks, sacrifice Booby Trap unless you discard a card.
(When the lives of Naya used to be short, he never lost his temper. Now he just
smiles)

https://www.urzas.ai/cards/?card_id=1ff17f7e-c112-4a58-8ebe-...

^ I was trying to get it to geneate something offensive, I confess.

Black Thunder
BBB
[Image: a threatening cloacked figure with pink thunder around its head]
Sorcery
Each player loses 1 life.
(Forged from the same material as the hilts of a star shell, the power of the
Raegstrom can't be blocked by armor.)

https://www.urzas.ai/cards/?card_id=56991776-6250-4940-ac29-...

Helm of Fire
1R
[Image: Kind of a melted helm, ok]
Artifact - Equipment - Equipment
Equipped creature gets +1/+0 and has haste.
Equip 1 (1: Attach to target creature you control. Equip only as a sorcery)

https://www.urzas.ai/cards/?card_id=96966793-2a0b-4b5d-9fb0-...

Sea of Knowledge
4U
[Image: A nondescript landscape, perhaps with thralls?]
Instant
Put target card from a graveyard onto the battlefield under your control
("Let the spirits of the dead join the living" - Nicol Bolas)

https://www.urzas.ai/cards/?card_id=96966793-2a0b-4b5d-9fb0-...

Word of Might
[Image: A nondescript figure perhaps with wings, in front of a colorful
landscape]
4G
Enchantment - Aura
Enchant creature
Enchanted creature gets +2/+2
("The law is one stone cannot be broken" - Xantcha, ancient astronomer)

https://www.urzas.ai/cards/?card_id=19b78a8c-a058-4adc-95b2-...

^ I only asked for "Enchantment" on this one but it correctly added "Aura" to
match its Ability.

Guardian of the Peace
[Image: A nondescript figure, perhaps in desert attire, in front of what could
be an abstract rendering of a modern city's skyline.]
WW
Creature - Human Soldier
{W}, {T}: Destroy target attacking or blocking creature.
(When the silver finds her feet, it grants her sisterhood. Only one person will
survive).
2/2

https://www.urzas.ai/cards/?card_id=7fa99ef1-8708-40b4-a387-...

^ In this card too the Tap symbol has a red hue. Why?

Scorching Sunset
5RR
[Image: abstract tiles that could be fields with what could be a burning palace
in the background]
Sorcery
Scorching Sunset deals 3 damage to any target.
(Once the flames begin to subside, the spark is forgotten)

https://www.urzas.ai/cards/?card_id=6b8d57c0-0477-41fe-96af-...

Mana Bomb
5
[Image: Maybe a kind of mock-oriental cauldron or boiler? Nondescript background
that could be attempts at reproducing ideograms?]
Artifact
{T}: Add {R}, {W}, or {U}
(Amass in corpse and feed it)

https://www.urzas.ai/cards/?card_id=6b8d57c0-0477-41fe-96af-...

Let's try a few curveballs.

Lightning Bolt
{R}
[Image: a nondescript view of what might be clouds with a yellow shape that
could be a bolt]
Instant
Lightning Bolt deals 3 damage to any target.
(If you can see the clouds, the lightning will strike.)

https://www.urzas.ai/cards/?card_id=0549337b-0b6b-4328-bbac-...

^ OK, so if we give it the name, cost and type of a known card...

Llanowar Elves
{G}
Creature - Elf Druid - Elf Druid
{T}: Add {G}
(As the evil spirit called the spirits of the dead, so the holy fire of
Llanowar, and our lifeblood, we bow in honor to them and the fire that would
never die)

https://www.urzas.ai/cards/?card_id=a64540fe-2d9c-49be-8381-...

Dark Ritual
{B}{B}{B}
[Image: nondescript hooded figures perhaps conducting a ritual]
Sorcery
Each player sacrifices a creature. You gain life equal to the life lost this
way.

https://www.urzas.ai/cards/?card_id=a64540fe-2d9c-49be-8381-...

^ Ah-hah! Dark Ritual has not seen nearly as many reprints as Bolt and Elves, so
it can't be reproduced as easily. My theory.

Honda Array
{P}{}{} (Empty mana circles)
[Image: could be a distorted rendition of a car?]
Factory - Car Factory - Vehicle
Horsepower (P/P) (P/P) (P/P) (P/P) (P/P) (P/P) .... (P/P) (

https://www.urzas.ai/cards/?card_id=363ad84e-4379-44f6-8447-...

^ It can sort of generate nonsense but not quite. Also, it can't close parens.
Typical.

Colossus of Rhodes
11
[Image: clearly a distorted image of a giant status in front of an abstract city
with sea]
Statue
When Colossus of Rhodes enters the battlefield, exile target artifact or
creature.
(Those who could tell of a scepter, one end of the alphabet, and dawn.)

https://www.urzas.ai/cards/?card_id=c0c106da-1fae-4733-bb89-...

^ What? What could those people do? Anyway it will happily generate cards with
nonexistent (base) types.

Donald Trump
{}{}{} (Empty mana circles)
[Image: could be Donald Trump and Imperial Palace Guards]
POTUS - Don'task target creature.
1{U},{T}: Draw a card

https://www.urzas.ai/cards/?card_id=962a7972-f6b4-4cfc-8200-...

areoiarg;iargea
a;eroigja;oerijg
[Image: a surrealistic depiction of people in kind of georgian dress?]
a;rgoijaer;oigjaerg - a;rgoijaer;oigjaerg
ifnd has access to look at the top card of target player's library.
(it's almost a month after they've shuffled)

https://www.urzas.ai/cards/?card_id=13a713b4-cc67-4434-8c31-...

^ They can't be playing a combo deck then.

Mark Rosewater
{} (Empty mana circle)
[Image: no idea. Something out of Bladerunner?]
Boss
2, {T}: Create a 0/1 colorless Clue artifact creature token.

https://www.urzas.ai/cards/?card_id=f1441b95-59a9-4527-a759-...

OK, I'm out of ideas.

Conclusions:
a) The ability text is not bad. Sometimes it makes sense, sometimes it doesn't.

b) It has absolutely no clue of the relation between mana costs and abilities,
but that's fine because neither does WoTC.

c) It will happily reproduce existing cards, but probably only if they have many reprints.

d) Forget about generating coherent images.

e) Forget about generating coherent reminder text.

For the last two tasks in particular, images and character text, my hunch is
that one would need to train on way, way more M:tG specific data. Or it might
need a separate system trained on a different prompt, because it doesn't seem to
find enough information in the generated card text or fluff.

Verdict: MaRo's job is still secure.

Also, having seen the attempt at M:tG Salvation that I think powers
RoboRosewater, this is not a substantial improvement over that. It would be if
it could produce meaningful art, but. No.