Cheapest priced copy (Kaldheim): $0.35 at Card Kingdom, near mint, their price list as of .
Guardian Gladewalker 
Creature — Shapeshifter · 1/1 · Common · Kaldheim · #174
Changeling (This card is every creature type.)
When this creature enters, put a +1/+1 counter on target creature.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
4 rulings from Wizards of the Coast
- 5 February 2021If an effect causes a creature with changeling to lose all abilities, it will remain all creature types, even though it will no longer have changeling. This is because changeling applies before the effect that removes it.
- 5 February 2021The subtype Shapeshifter that appears on the type line is mostly there to reinforce the flavor. A creature card with changeling is just as much an Elf, a Dwarf, a Sliver, a Goat, a Coward, and a Zombie as it is a Shapeshifter.
- 5 February 2021If an effect causes a creature with changeling to become a new creature type, it will be only that new creature type. It will still have changeling; the effect making it all creature types will simply be overwritten.
- 5 February 2021Changeling is a characteristic-defining ability. It functions in all zones, not only while a card that has it is on the battlefield.