Modern Horizons 3 contains the 5 basic lands (Plains, Island, Swamp, Mountain, and Forest) with variant treatments, plus an uncommon Snow-Covered Wastes (included as one of the 101 uncommons) with its variant treatments
You may not be able to pull off the companion ability every time but you'll still be giving a good boost to your team and letting your creatures play offense and defense
How about changing it to a normal spell card, and the monster to something like "This card can only be special summoned by the effect of "Spell's name""
Waterproof Protection: Made of PP plastic to protect cards from falling out and water damage
This mechanic is very similar to how charge counters were used in the Scars of Mirrodin block, where you could have diverse implementations in cards like Shrine of Burning Rage, Tangle Wire, and Lux Cannon