Reno the Water Dice Magician is a great nuker with AoE ignore defense skill in Summoners War.
Like all others Dice Magicians, his skills are based on RNG (Random Number Generator): whenever he attacks he rolls from two to four dice, depending on the skill used.
The first skill grants two weakening effects based on the following list:
 result of one die is from 1 to 3 included = no effects applied on target;
 result of one die 4 = Unrecoverable for 2 turns;
 result of one die 5 = Decrease Defense for 2 turns;
 result of one die 6 = Increased chances of missing (glancing hit) for 2 turns.
Moreover Reno gains another turn if the 2 dice have the same result: 1 and 1, 2 and 2, and so on.
That means that he has 1/6 (16,67%) of chance of getting another turn with the first skill.
Reno's second skill (the same as his dark twin Monte) is an AoE attack with chance to randomly apply the same weakening effects as first skill: Unrecoverable state, Decrease Defense and Increased glancing hits. Also in this skill two dice are rolled: increasing the sum of the two numbers rolled, more effects are applied on targets. The probability of get a result is as follows:
 sum is 2 from 1+1, which means 1/36 = 3%
 sum is 3 from 1+2, 2+1, which means 2/36 = 6%
 sum is 4 from 1+3, 2+2, 3+1, which means 3/36 = 8%
 sum is 5 from 1+4, 2+3, 3+2, 4+1, which means 4/36 = 11%
 sum is 6 from 1+5, 2+4, 3+3, 4+2, 5+1, which means 5/36 = 14%
 sum is 7 from 1+6, 2+5, 3+4, 4+3, 5+2, 6+1, which means 6/36 = 17%
 sum is 8 from 2+6, 3+5, 4+4, 5+3, 6+2, which means 5/36 = 14%
 sum is 9 from 3+6, 4+5, 5+4, 6+3, which means 4/36 = 11%
 sum is 10 from 4+6, 5+5, 6+4, which means 3/36 = 8%
 sum is 11 from 5+6, 6+5, which means 2/36 = 6%
 sum is 12 from 6+6, which means 1/36 = 3%
Getting a higher sum, grants more effects on targets. Additionally, just like the first skill, getting the same result with the two dice grants another turn (16,67%).
Compared to Brownie Magicians (like Orion), Dice Magicians have lower chance of getting another turn on first skill, but also the second skill can make them gain another turn.
Finally, the third skill is the second skill (the first one is Lushen's third skill Amputation Magic) in the game that (can) deal damage ignoring defense to all enemies: it hits all enemies four times and if a dice rolls the same result as one dice before, that attack will ignore defense. Moreover the damage icreases as the number rolled increases.
The results of the dice rolled, in order to ignore defense, they do not have to be one after another. It is enough if any number appears twice or more, no matter which dice.
So the probability of getting ignoring defense damage is as follows:
 Chance of all 3 proc: (1/6)3 = 0.5%;
 Chance of at least 2 proc: 10.277(chance of no proc) 0.625(chance of exactly 1 proc) = 9.8%;
 Chance of at least 1 proc: 1 0.277 = 72.3%;
 Chance of NO proc ignore defense: (5/6)(4/6)(3/6)= 27.7%.
It's a pretty good chance of getting at least one ignore defense damage.
Reno is good for ToA on a Despair build since he has two AoE skills plus AoE increase glancing hits (which is good for higher level of Trial of Ascension) and in Raid Battle on Revenge runes for his first skill (all three effects are good against Raid boss battle)
And of course Reno is good in PvP, because with his third skill can be a really good substitute for Lushen in offense: additionally can be very good for players that rely on double Lushen teams, since Reno is water element, making him a viable solution to nuke Kumar, Rakan or other fire tank based teams in Arena.
Violent attacker: Violent/Blade or Violent/Fight  SPD / %Crit dmg / %ATK or %ATK / %Crit dmg / %ATK
Crowd Control: Despair/Focus or Despair/Accuracy  SPD / %HP / %HP or SPD / %Crit dmg / %ATK
AoE Nuker: Rage/Blade or Fatal/Blade  SPD / %Crit dmg / %ATK or %ATK / %Crit dmg / %ATK
Revenge build: Rage/Revenge or Violent/Revenge  SPD / %Crit dmg / %ATK or %ATK / %Crit dmg / %ATK
All builds with SPD, %Crit rate, % ATK as main substats.
Indepth stats about Reno could be retrieved on SWARFARM
Rating by users: 4.11 / 5 based on 14 reviews
Monster Type: attack
Speed  CRI Rate  CRI Dmg  Resistance  Accuracy 

102  15%  50%  15%  0% 
Form  Stars  Attack  Defense  Hp 

Awakened 
Min: 248 Max: 422 
Min: 189 Max: 321 
Min: 2,880 Max: 4,905 

Awakened 
Min: 337 Max: 573 
Min: 257 Max: 436 
Min: 3,915 Max: 6,660 

Awakened 
Min: 459 Max: 780 
Min: 349 Max: 593 
Min: 5,325 Max: 9,060 

Unawakened 
Min: 220 Max: 374 
Min: 178 Max: 303 
Min: 2,670 Max: 4,545 

Unawakened 
Min: 299 Max: 509 
Min: 242 Max: 412 
Min: 3,630 Max: 6,180 

Unawakened 
Min: 407 Max: 692 
Min: 329 Max: 560 
Min: 4,935 Max: 8,400 