Champion Idea: Seliah The Celestial Princess

So I had an idea a while back for a champion that could essentially merge with another allied champion to become to increase their strength, while retaining their ability to freely cast spells. While my original concept has changed a lot since then, I think I've ironed out all of the kinks and made as balanced a concept as I could without being an experienced concept artist. So I've decided to post my idea here on the forums. Seliah is meant to be played as an AP support who specializes in making her fellow allied champions an even bigger threat than they were originally, and does this granting them bonus stats, plus adding in Seliah's own abilities into their arsenal. Once Seliah's ult has been activated, enemy champions will suddenly find them selves fighting what is essentially two champs in one.

Seliah The Celestial Princess

P: Blessed Seliah grants nearby allied champions bonus magic damage on their basic attacks based on her level. (10 magic damage at level 1 + 2.5 magic damage x each subsequent level. This bonus is increased by 25% for Championed allies).

Q: Guiding Light (15/14/13/12/11 second cool-down.) (80/95/110/125/140 mana.) Seliah fires a skill shot that damages all enemy units struck (40/45/50/55/60 + 10% of Seliah's AP) and reveals them. If Seliah or an allied champion basic attacks a revealed enemy, their first attack deals bonus magic damage ((90/120/150/180/210 + 80% of Seliah's AP)This only applies to the first allied attack. If another allied champion attacks after the fact, no bonus damage is applied).

W: Consecrated Ground (25/23/21/19/17 second cool-down.) (100/110/120/130/140 mana.) Seliah creates a circular A.O.E. field that after a 1 second delay damages (120/140/160/180/200 + 60% of AP) and slows all enemies struck by 80%.

E: Radiant Shield (30/27/24/21/18 second cool-down.) (150 mana.) Seliah creates a shield around an allied champion that absorbs damage (130/160/190/220/250 health) for 3 seconds. While the shield is active, the shielded ally is passively healed for 2% of their maximum health + 40% of Seliah's AP as a flat amount per second. Should the shield be destroyed, the shielded ally will be healed for half of the health that hadn't been healed yet.

R: Heaven's Champion (60/50/40 second cool-down.) (120/130/140 mana.) Selliah targets an allied champion, becoming untargetable and granting them 20% of her maximum health, as well as 5/10/15% bonus movement speed decaying over 5 seconds, 8/10/12% cool-down reduction, and 5% damage reduction for 8 seconds. While active, Seliah becomes untargetable, but follows her Championed allies movements. Should Seliah's Championed ally lose health equal to 50% of the max health, the skill is canceled. Seliah can still freely cast spells while untargetable but cannot use basic attacks.

-Edit: Now with more counterplay. Mana costs added.