Lord of Atlantis + Lich-Knights' Conquest

Outrider of the Sunless Depth
Creature - Merfolk Knight
Flash
When this creature enters, target nonland permanent's owner puts it on top of or the bottom of their library. If you controlled that permanent, mill three cards. You may put an artifact, enchantment, or Merfolk card milled this way into your hand.
2/2

Lich-Knights' Conquest + Plains

plains + demonic consultation

Consultationville
Land
, Exile the top card of your library: Add one mana of any colour of a card exiled this way. Activate this ability only any time you could cast an instant.

You have to be joking...

Demonic Consultation + Mountain

Gibbering Consultation
Instant
Choose a card name. Exile cards from the top of your library until you exile the named card. You may play that card until the end of your next turn.
The nonsensical utterances echoed in Mila's head until they were all she hear or say.

Mountain + Aerialephant

Summit Mounter
Creature - Elephant Scout
Whenever this creature attacks a player that controls a Mountain, put a stun counter on it.
Whenever you remove a stun counter from this creature, up to one target other creature you control gains Mountainwalk until end of turn.
3/3

So you're not going to believe this

Aerialephant + Island

Pachyderm Privateer
Creature - Elephant Pirate
When ~ enters the battlefield, create a treasure token.
You may sacrifice treasure rather than pay a crew cost when crewing vehicles. If ~ is untapped when a vehicle deals combat damage to a player, create that many treasure tokens.
If you control no treasure, Vehicles you control have Islandwalk.
[3/3]

was tempted to keep randoming until I got a basic land, but

Island + Savage Surge

Strange Surge
Instant
Target creature gets -2/+2 until end of turn. You may tap or untap that creature.

savage surge + atraxa, praetors' voice

Atraxa, Praetors' Voice + Immortal Phoenix

Phyrexian Phoenix

Creature - Phoenix
Flying
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
When Phyrexian Phoenix dies, return it to its owner’s hand and proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Inside a phoenix, a fire burns brightly from within but even those flames are not powerful enough to purge the contagion once it spreads.
3/3

Immortal Phoenix + Insatiable Frugivore

Feathered First Frost
Creature — Elemental Bird
Flying, menace
Whenever you exile this card from your graveyard while foraging, return it to your hand.
She barely grazes the land, but the gentle flutter across the nose is a dire omen.
5/3

insatiable frugivore + colorful feiyi sparrow

Colorful Feiyi Sparrow + Sepulcher Ghoul

Pyreborn Phoenix
Creature —Phoenix
Flying
, Sacrifice a creature or artifact: This creature gets +2/+0 until end of turn.
When this creature dies, if its power is 4 or greater, return it to your hand.
1/3

Sepulcher Ghoul + Windbrisk Heights

Unholy Sepulcher
Land
Hideaway 4 (When this land enters, look at the top four cards of your library, exile one face down, then put the rest on the bottom in a random order.)
This land enters tapped.
: Add .
, : You may play the exiled card without paying its mana cost if you sacrificed three or more creatures this turn.

Windbrisk Heights + Wakedancer

Morbid Legionnaire
Creature - Zombie Soldier (R)
Battalion - Whenever this creature and two other creatures attack, this gains deathtouch, indestructible, and "whenever another nontoken creature dies, create a tapped 2/2 black Zombie creature token" until end of turn.
His soldiers followed him to the grave and beyond.
[4/3]

Wakedancer + Winter Orb

Curse of Wandering
Enchantment - Aura Curse
Enchant player
Whenever enchanted player taps a land they control for mana, they may put a stun counter on it. If they don't, put an awakening counter on this Curse.
At the beginning of your upkeep, you may remove all awakening counters from this Curse. If you do, return a creature card with mana value equal to or less than the number of counters you removed this way from your graveyard to the battlefield. That creature is a Zombie in addition to its other types and has decayed.
The soul of Amonkhet clings to her children and refuses to let them leave her.

Winter Orb + Black Sun's Zenith

Northern Wind

Sorcery
Tap X target creatures. Distribute X stun counters amongst creatures tapped this way. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Unsuspecting travellers of the Artic Plains dream of exploration and conquest, but in the end, they all beg for Summer.