Waves from the side attk: not sure how to dodge other than to not be there
Submerge: The water looks different from normal where she reappears, get away from it
Waveform: tries to run you over, get out of the way
Summoning: Not much to say, just try to stay alive
Ultimate: There is a trick to it, stay to the side and move in increments, it seems to leave openings that are predictable and you can move accordingly to dodge.
Water Blasts: Not much really, slow so they can be dodged
Charge: とりあえずポータルに逃げ込め。Mystic Veil, or get out of the way. It hurts, but there isn't really anything to do about it.
Grabby-thingy: とりあえずポータルに逃げ込め。Hits for about 750-1k iirc, can't be dodged. Turn on Veil asap in case he starts banging on you and hope you grabbed some speed upgrades.
Ult: Stick to the portals. Watch where he is; if possible, put the portal in between you and him, keeping in mind that you can't actually be behind the portal, only beside it.
Light: Medivh ULTさえ対応できればそう怖い相手ではない。
Judgement - Try to avoid it, keep away from him.
Divine Serpent - If you're lucky this will miss you, you can't really dodge it but you can stay to the sides.
Spinning Bar Thing - You can either get away from him or run around while it chases you.
Teleport - Dodge the green ball, if he lands on you you get telefragged.
Light Volcano - I'm still wondering exactly how this was made, but that's not the point. The orbs of light probably won't hit you, but they do deal significant damage when they hit the ground.
Ultimate (Seal of Light) - 全員のHPが1になり、一定時間後回復量に応じてダメージ。"seal of light"の文字が大量に吹き出し終わると同時に即無敵を使えば回避可能。またpaladinのユニーク装備による完全回復等でも耐えれる。さらにIce MageのShieldでも防げる。