Sanctification:

Effect:

Safeguard: Grants yourself and nearby Allied Heroes a 250 (+12% of Caster's Maximum Health) shield for 3s. While the shield holds, Heroes gain 60% tenacity - 120s CD.

Reason:

While Phase doesn't get as much value out of this crest compared to tanks like Rictor and Narbash due to their higher maximum health, I still believe Sanctification is a solid choice on Phase seeing as how team fights and even the laning phase alone can be pretty CC heavy.

Wellspring:

Effects:

Vital Waters: Casting an ability heals nearby Allies for 20 (+10% Magical Power) over 2s.

Soothing Waters: Vital Waters heals an additional 10% of your lowest Ally's maximum health. Basic attacks against Enemy Heroes reduce the cooldown of Soothing Waters by 1s - 20s CD.

Reason:

Wellspring provides an AOE heal that continues as long as you keep using abilities, as well as a burst heal which allows Phase to quickly top someone back up or to help sustain them during or after battle. The effects of Wellspring also proc the effects of Crystal Tear for anyone affected by its effect.

Tainted Scepter:

Effects:

Blighted Spells: Dealing magical damage to an Enemy Target reduces their Healing by 40% for 4s.

Malice: Every second, gain a stack of Malice, up to a maximum of 15. Damaging an Enemy Hero with an ability consumes Malice to deal 5 (+1% magical power) magical damage per stack. Takedowns grant maximum stacks of Malice instantly.

Reason:

Tainted Scepter provides Phase with a consistent form of Anti Healing whilst also increasing the value she gets from her healing and from the shield granted by Sanctification due to the increase of health and magical power.

Vanguardian:

Effects:

Vanguard: Receiving damage from an Enemy Hero grants you 30 physical armor and 30 magical armor for 4s. While active, damage received from Enemy Heroes refreshes the duration - 60s CD.

Guardian: Nearby Allied Heroes gain 10 physical armor and 10 magical armor.

Reason:

Vanguardian provides physical and magical armor to Phase and her allies. Additionally, it increases her max health, which in turn increases the shield provided by Sanctification.

Dreambinder:

Effect:

Chilling Spells: Damaging abilities Slow affected Units by 25% (10% for DoT Abilities) for 1s.

Reason:

Dreambinder increases the initial and stacking slow of Energy Lance making it harder for enemies to escape, whilst also increasing the value she gets from her healing and from the shield granted by Sanctification due to the increase of health and magical power.

Final stats:

Shield provided by Safeguard (Sanctification's active):

844

Without link and without Fangtooth:

Essence Catalyst: 183
Psychic Flare: 434
Energy Lance: 323
Pulse Bolt: 84

While linked without Fangtooth:

Essence Catalyst: 191
Psychic Flare: 456
Energy Lance: 338
Pulse Bolt: 90

While linked with Fangtooth:

Essence Catalyst: 198
Psychic Flare: 476
Energy Lance: 352
Pulse Bolt: 95