Ancient Apparition is a very popular pick when you see self regen and healers on the enemy team, but can be useful even in other lineups. Here are some tips to make the most of him -

1. Cold feet often to make cores run out of the lane and lose cs. Also cold feet cores mostly immobile cores in teamfights.
2. Spam ice vortex whenever possible to amp magic damage, provide vision in trees and fog of war, and slow enemies running away.
3. Auto cast chilling touch most of the time for more damage. Try to aim for low health heroes in teamfights to finish them off fast.
4. Ice blast makes you have a global presence, so keep an eye on the map and fights that break out at places away from you. Plan ahead and fire ice blasts in places where you think the enemies will be.
5. In teamfights where you're present, fire it ahead of you onto the group of enemies for most damage.
6. Aim to hit fountains and shrines if enemies tp out in low health.
7. Also use ice blast to initiate ganks for quick and easy kills.

Be an apparition no longer, rise with your true power to end the future of the enemy team!

Feel free to leave comments on the guide if you have any questions. :)