Sleipnir’s Boon:

You have proven yourself a great steed and worthy of Sleipnir’s blessing.  You now have the following abilities:

Celestial Wild Shape:

• You can expend one use of Wild Shape to transform into a Pegasus
• You can expend two uses of Wild Shape to transform into a Unicorn (without the use of legendary actions).

Sermon from the Mount:

• Whilst your Wild Shape is active and you are acting as a mount, you can choose one creature mounted upon you to benefit from your Wisdom Saving Throw bonus (rather than their own).