If Mordenkainen's celerity was cast by the same person moments before a spell such as feather fall, fly, haste, jump, levitate, or spider climb, the magical speed granted by that spell and its duration increased by a factor of 25%. In the case of feather fall, the falling speed could also be reduced by the same amount if the caster so desired. Additionally, a casting of haste following the spell affected more creatures.
- Mark Middleton et al (March 1998). Wizard's Spell Compendium Volume Three. (TSR, Inc), p. 592. ISBN 978-0786907915.
- Dale Donovan (January 1998). Cult of the Dragon. (TSR, Inc), p. 64. ISBN 0-7869-0709-6.
- Sam Witt (January 1994). The Complete Sha'ir's Handbook. (TSR, Inc), pp. 124–125. ISBN 978-1560768289.
- Cook, Findley, Herring, Kubasik, Sargent, Swan (1991). Tome of Magic 2nd edition. (TSR, Inc), p. 30. ISBN 1-56076-107-5.