River Serpent

Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.) Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

+2: Until your next turn, up to two target creatures each have base power and toughness 0/3 and lose all abilities. −2: Target player draws two cards. Until your next turn, instant, sorcery, and planeswalker spells that player casts cost 2 less to cast. −8: Target player gets an emblem with "Whenever you cast an instant or sorcery spell, copy it. You may choose new targets for the copy." Partner with Rowan Kenrith Will Kenrith can be your commander.

Flying, vigilance T: When target creature other than this creature dies this turn, return that card to the battlefield under your control.

2, Exile a nonland card from your hand: Put four time counters on the exiled card. If it doesn't have suspend, it gains suspend. (At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. If it's a creature, it has haste.)

Protection from red Elemental creatures you control get +1/+1. When this creature enters, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue. (Each U in the mana costs of permanents you control counts toward your devotion to blue.)

Flying

Flying, first strike, vigilance, trample, haste, protection from black and from red

Forests you control are 1/1 green Elf creatures that are still lands. 1G, Sacrifice an Elf: Target creature gets +3/+3 until end of turn.