The elementalist part of this build for Glacius uses material from Vast Kaviya (available via Kickstarter this week only).

Glacius

Medium humanoid (water genasi), chaotic neutral fighter (battlemaster) 11/monk (1)/elementalist (water) [V] 5
Armor Class 19 (Wisdom, martial arts stances)
Hit Points 104 (11d10+6d8+17)
Speed 40 ft., swim 40 ft.

STR	DEX	CON	INT	WIS	CHA
18 (+4)	16 (+3)	12 (+1)	10 (+0)	16 (+3)	8 (-1)

Saving Throws Str +10, Con +7
Skills Athletics +10, Intimidation +5, Perception +9, Survival +9
Damage Resistances acid, cold, force
Senses darkvision 60 ft., passive Perception 19
Languages Aquan, Common, Primordial
Challenge 12 (8,400 XP)

Action Surge (1/Short Rest). Once on his turn, Glacius can take an additional action on top of his regular action and a possible bonus action. 

Amphibious. Glacius can breathe both air and water.

Conjure Minor Elementals (1/Short Rest). Glacius can innately cast conjure minor elementals to summon water elementals, requiring no material components or concentration. 

Elemental Control. Glacius can use a bonus action to affect water (as mage hand), or use a bonus action to conjure a handful of water. He can use this ability to craft wondrous and impressive displays, resist dehydration, or douse small flames.

Elemental Touch. Glacius can use an action to wreathe his hands in water for 1 minute, dealing an additional 1d8 cold damage when he hits with an unarmed strike (included below). 

Elemental Weaponry. Glacius can use his Elemental Touch to deal additional damage when wielding a melee weapon or ranged weapon. When wielding a weapon with the ammunition property, his Elemental Touch automatically replaces the normal ammunition (creating ice bullets for slings, water bolts for crossbows, and the like). 

Feat: Mobility. Glacius can Dash through difficult terrain without requiring additional movement. Whenever he makes an attack against a creature, he doesn’t provoke opportunity attacks from that creature until the end of his turn.

Fighting Style: Archery. Glacius gains a +2 bonus on ranged attack rolls.

Fluidity. Glacius has advantage on Strength (Athletics) checks made to swim. In addition, he can automatically succeed on Dexterity (Acrobatics) checks and Dexterity saving throws made to avoid slipping or losing his balance.

Genasi Legacy. Glacius knows the shape water cantrip and he can cast create or destroy water as a 2nd-level spell once with this trait, regaining the ability to do so when he finishes a long rest. Constitution is his spellcasting ability for these spells (spell save DC 15).

Indomitable (1/Long Rest). Glacius can reroll a saving throw that he fails but must use the new roll.

Like Water. Glacius knows the ray of frost cantrip, using Strength as his spellcasting ability (+10 to hit with spell attacks).

Maneuver Master (5d10/Short Rest). Glacius can expend a maneuver dice to perform a single maneuver with an attack.

• Counter. Glacius uses his reaction to make a melee attack against a creature that misses him with a melee attack, dealing 1d10 additional damage on a hit.
• Feint. Glacius can use his bonus action to feint against one creature within 5 feet. He has advantage on his next attack roll against that creature as long as it before the end of his turn. On a hit he deals 1d10 additional damage.
• Maneuver. On a successful hit with a weapon attack, Glacius deals 1d10 extra damage and chooses a friendly creature that can see and hear him. That creature can move half its speed by using its reaction. This movement does not provoke opportunity attacks from the target of Glacius’ attack. 
• Sweep. Glacius chooses a creature adjacent to him target and within his reach and on a hit, the adjacent creature takes 1d10 damage (of the same type as the weapon attack).
• Trip. Glacius deals 1d10 additional damage and if the target is a creature of Large size or smaller, it makes a DC 18 Strength saving throw or is knocked prone.

Martial Arts. Glacius can use Dexterity instead of Strength for the attack and damage rolls of his unarmed strikes and monk weapons. In addition, when Glacius uses the Attack action with an unarmed strike or a monk weapon on his turn, he can make one unarmed strike as a bonus action.

Second Wind (1/Short Rest). On his turn, Glacius can use a bonus action to regain 1d10+11 hit points.

Water Soul. Glacius can stand on and walk across liquid surfaces as if they were solid ground. 

ACTIONS

Extra Attack. Glacius attacks three times when he takes the attack action (using a bonus action he can attack a fourth time using Martial Arts).

Unarmed. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 6 (1d4+4) bludgeoning damage plus 9 (2d8) cold damage.

REACTIONS

Stance of the Frozen Flower (3; 6/Long Rest) [M]. As a reaction, Glacius can flash-freeze the air around his body in protective petals of ice. These ice petals have 12 hit points and any damage he takes before the end of his next turn is subtracted first from this pool of hit points.

 

M = Mists of Akuma

V = Vast Kaviya