Mikasi is one of the three Combat tutors, known to be the instructor for both Magic and Runecraft. She is located on a small hill north of Lumbridge Castle.
Every 30 minutes, players can claim 30 air runes and 30 mind runes for free, regardless of their Magic level, as long as there are none in their bank or inventory. Players also need to not have claimed training arrows from the Ranged combat tutor in the last 30 minutes either.
It is possible to claim more air and mind runes even if the player are already owns some. The player must drop all the air and mind runes they own and then ask the tutor again for runes.
For players looking to train Magic with these runes, casting Earth Strike with a staff of earth is a good strategy. It gives more experience than Wind Strike, yet the spell will have the same rune cost of one air rune and one mind rune.
As of an update on 17 August 2017, players can talk to her to toggle the option to automatically add runes they pick up off the ground to their rune pouch if they already have that kind of rune in it and have enough space for the picked-up runes.