Rionya is a unique commander combining spell slinging with storm and creature copies. Rionya decks are filled with cheap instant and sorcery cantrips and tends to win the game with multiple copies of a single creature they control.
Rionyas ability gets stronger and stronger as the copied creatures mana value goes higher. Due to this, Rionya is a proper commander for expensive tribals, with not-enough tribal synergies in mono red.
Burn is reds primary mechanics. Red can deal massive amounts of damage to single target or deal multiple amounts of single damage to multiple targets. Burn decks aim to win with massive outbursts of big, uncounterable and unpreventable damage to opponents (and sometimes the burn player itself).
Goblins are reds main creature type and gets new support from almost every set. Goblin tribals focus to create many 1/1 goblin tokens and make them bigger with Goblin lords, buffing them up and giving them haste. Often the decks run multiple different sac outlets to either burn players or receive extra value from the tokens.
Dragons, alongside Goblins, are reds primary creature types. Dragons are reds strongest creatures and most of the expansions have some kind of red dragon in them. As dragons are expensive to cast, dragon tribal decks run multiple cost reduction effects and have ways to cheat the expensive dragons on the battlefield.
Giants are expensive and big creatures in red. Giants are red secondary creature types, and a tribal deck in mono red is difficult to pull off. Giants tend to receive some new creatures every now and then so giant tribals are getting close to the limit, where they are solid tribal.
Rionyas ability grows stronger the more instants and sorceries you have cast during your turn. Here is a list of great cantrips in mono red, allowing you to increase the rionya-storm count and find the necessary lands.
As Rionya is a center piece of the deck, Rionya draws lots of heat and target removals. Mono red is not the best color against removals and is weak in terms of permanent graveyard recursion. Therefore Rionya decks best solution against removals are change-target spells: as bonus you increase the Rionya storm count with all of these!