Level Up is a keyword ability.
702.86. Level Up
- 702.86a Level up is an activated ability. “Level up [cost]” means “[Cost]: Put a level counter on this permanent. Activate this ability only any time you could cast a sorcery.”
- 702.86b Each card printed with a level up ability is known as a leveler card. It has a nonstandard layout and includes two level symbols that are themselves keyword abilities. See rule 710, “Leveler Cards.”