Fortify is a keyword ability.
This ability has only been featured on one card so far, Darksteel Garrison.
- 702.66a Fortify is an activated ability of Fortification cards. “Fortify [cost]” means “[Cost]: Attach this Fortification to target land you control. Activate this ability only any time you could cast a sorcery.”
- 702.66b For more information about Fortifications, see rule 301, “Artifacts.”
- 702.66c If a Fortification has multiple instances of fortify, any of its fortify abilities may be used.