Other than restrictions on heroes/troops and Special Rules, the Raids themselves in Weekly Raid Tournaments work the same way as regular Raids.
Each day, you’ll be able to attack up to 5 teams.
The flags used for Raid Tournaments are separate from regular Raid flags.
NOTE: Kills in Raid Tournaments count toward your Wanted: Heroes Raid Chest, so Raid Tournaments also effectively give you extra flags to potentially help fill your chest.
One notable difference to Regular Raids — you can’t reroll.
For the whole of the Tournament, you have 4 “Lives.” Each time you lose a Raid, you lose one life.
The lives do not reset across days of the Tournament. Once you’d lost 4 times at any point during the Tournament, you are out.
If you choose, you can pay some gems to reset your lives after 4 losses — but your score and ranking would still be lowered because of the losses. Paying to reset your lives does NOT give you an advantage from the Raids you’ve already fought. It simply allows you to continue using your normal 5 flags per day and not be “out” of the Tournament.
There is no way to buy additional flags. So everyone ultimately had the same number of maximum flags to use for attacks during the Tournament. The only thing gems allow you to do is continue playing if you’ve used up all of your lives.
CAVEAT: How this worked in beta changed SEVERAL times during testing. It’s very possible we’ll see how all of this works evolve over time, much like Alliance Wars have changed many times since initial release.
Matchmaking
This is an area of the Raid Tournaments that’s obviously had significant problems, and continual revision.
The developers are continuing to work to refine and improve how matchmaking works, so we don’t know exactly what to expect yet, but they’ve set up a Raid Tournament Change Log, which you can monitor for updates.
Matchmaking for Attacks
Click for details on Matchmaking for Attacks
As of the Third Raid Tournament, initial matchmaking was based on your Top 5 strongest heroes that qualified for the Tournament’s rarity and elemental restrictions:
This was slightly amended as of the Fourth Raid Tournament:
The difficulty of the opponents reduced slightly in the beginning of tournaments.
Matchmaking for Defense
Click for details on Matchmaking for Defense
As of the Sixth Raid Tournament, matchmaking for Defense teams was changed again:
Further improvements to the distribution of attacks, especially for the top players.
Keep in mind that if you’re in the top, your defense team will receive more attacks. This is due to the fact that there is a small number of top defense teams that are good matches for a large number of top attackers. We try to prioritize choosing a good opponent over choosing a too easy or too difficult opponent that hasn’t been attacked as much. We have also implemented a limit on how attacks count towards your Defense Grade. After the first five attacks of the day, only one attack per hour counts towards the grade.
Changes to the starting difficulty of opponents your defense team faces.
It is no longer based on the defense team you pick, but your best heroes that match the tournament requirements. We’ve brought this rule back because we want to encourage players to choose the best defense team they can, and thus provide a better challenge to their opponents. Due to the way the Team Power is calculated it was possible, for example, to pick a defense team of two fully leveled, fully ascended heroes that were on paper equal in Team Power with a full team of lower rarity heroes, but in practice that full team would be defeated in most cases.
Scoring
Click for details on Scoring
NOTE: Hat tip to @DracoLovesRi for pointing out that there haven’t seemed to be “extra points” for a victorious attack:
New as of the Second Raid Tournament:
Defense Team Grade
Click for How Defense Team Grade Works
I found this was actually very clear and useful — and I think provides some insights into regular Raid Defense Teams too.
The grades are assigned based on a percentage of wins by your Defense Team:
The Defense Grade is determined based on the win percentage of your Defense Team. At the end of each Battle Day, you receive points based on your grade.
Percent Won
Grade
Points
60%
A
900
50%
B
650
40%
C
500
30%
D
400
0%
E
200
My Personal Take on This:
The top grade in this approach was awarded to a Defense Team that won 60% of the time. To me, that’s a good confirmation of what many of us have long accepted: Raids are unfair, but not for the reasons you think - Raids MASTER — that is, they heavily favor the attacker, and even a top-notch Defense Team will lose much of the time.
Restrictions
Each Week can have restrictions on:
Hero and troop rarity — e.g. only allowing 3* heroes and 2* troops or below
Elements — e.g. no red/fire heroes allowed
Special Rules
Click for details on Special Rules
Each week has ONE Special Rule in effect.
(At least in beta; it’s possible live Tournaments may sometimes have multiple Special Rules at once. If that ever happens, I would be surprised if we see that before core elements like matchmaking are working properly, so I anticipate a single Special Rule for the foreseeable future.)
The possible Special Rules are:
Whichever Special Rule is in effect for a given Tournament remains in effect for the entirety of that Tournament.
The Special Rule affects both Defense and Offense teams.
Some Clarifications/Expansions
Rush Attack makes all hero specials of any speed Very Fast — it doesn’t require Very Fast heroes, it turns all heroes into Very Fast heroes. Heroes that are normally Slow or Average can become quite powerful in this setting.
Bloody Battle makes any healing effects do nothing. It doesn’t prohibit healers, it just prevents the healing portion of their special skill from having any effect.
Buff Booster adds a stackable 20% attack buff to each hero for each active buff on that hero. Using heroes with special skills that grant buffs or multiple buffs can lead to very high attack boosts. These buffs stack with each other and normal attack buffs.
Rewards
The initial loot for Raid Tournaments was quite excellent in the top tiers, but that loot was only available during the very first Raid Tournament.
Click for Archive of First Tournament's Loot, before reduction
Acronyms in this table:
AM: Ascension Materials
EHT: Epic Hero Token
ETT: Epic Troop Token
Any of the tiers starting at top 75% have a chance for ascension mats.
Here’s the current breakdown for ascension mats, tokens, and Emblems (for simplicity, I didn’t include the Flasks, Atlantis Coins, Battle Items, and Crafting Materials that are in loot in addition to these):
Tier
AM Chance
EHT/ETT Chance
Emblems Chance
75-100%
0
0
1 Draw: 100% x1
50-75%
1 Draw: 5% 3*
1 Draw: 5% EHT, 15% ETT
1 Draw: 20% x3, 30% x2, 50% x1
25-50%
1 Draw: 18% 3*, 2% 4*
1 Draw: 15% EHT, 25% ETT
1 Draw: 40% x5, 60% x3
10-25%
1 Draw: 22% 3*, 3% 4*
2 Draws: 20% EHT, 40% ETT
1 Draw: 40% x5, 35% x10, 25% x20
5-10%
2 Draws: 45% 3*, 5% 4*
2 Draws: 25% EHT, 45% ETT
1 Draw: 10% x50, 20% x30, 30% x20, 40% x10
1-5%
2 Draws: 95% 3*, 5% 4*
2 Draws: 40% EHT, 60% ETT
1 Draw: 5% x100, 30% x50, 30% x30, 35% x20
Top 1%
2 Draws: 90% 3*, 10% 4*
3 Draws: 50% EHT, 50% ETT
1 Draw: 25% x100, 50% x35, 30% x40
As of the Second Raid Tournament, loot was reduced due to problems with the Raid Tournaments. This was initially indicated as being temporary while issues were fixed:
The loot as of the Seventh Raid Tournament was very slightly tweaked. For discussion about this, please see this thread: The New, NEW Raid Tournament Loot
Click for details on Current Loot effective on the 166th Raid Tournament
Acronyms in this table:
AM: Ascension Materials
EHT: Epic Hero Token
ETT: Epic Troop Token
Gray: Summon Token
Any of the tiers starting at top 75% have a chance for ascension mats.
Here’s the chances of the current breakdown for ascension mats, tokens, and Emblems, coins, tomes, battle items and crafting materials
Tier
AM
EHT/ETT
Emblems
Aether
Coins
Tomes
Battle items
Crafting materials
75-100%
-
-
1 Draw: 100% x3
-
-
-
-
3 Draws: 50% 2* 50% 1*
50-75%
1 Draw: 1% 3* 50% 2* 49% 1*
1 Draw: 1% EHT 3% ETT 96% Gray
1 Draw: 100% x5
-
1 Draw: 20% x3 30% x2 50% x1
-
1 Draw: 2% 4* 4% 3* 35% 2* 59% 1*
1 Draw: 2% 4* 4% 3* 35% 2* 59% 1*
25-50%
1 Draw: 20% 3* 40% 2* 40% 1*
1 Draw: 3% EHT 5% ETT 92% Gray
1 Draw: 100% x10
3 Draws: 67% 3*
1 Draw 10% x5 20% x3 70% x2
-
1 Draw 4% 4* 6% 3* 35% 2* 55% 1*
1 Draw 4% 4* 6% 3* 35% 2* 55% 1*
10-25%
1 Draw: 25% 3* 40% 2* 35% 1*
1 Draw: 4% EHT 8% ETT 88% Gray
1 Draw 100% x20
1 Draw: 10% 4*
3 Draws: 3* 64%
1 Draw: 15% x5 25% x3 60% x2
-
1 Draw: 4% 4* 8% 3* 35% 2* 53% 1*
1 Draw: 4% 4* 8% 3* 35% 2* 53% 1*
5-10%
1 Draw: 1% 4* 45% 3* 54% 2*
1 Draw: 5% EHT 9% ETT 86% Gray
1 Draw: 100% x30
1 Draw: 9% 5*
2 Draws: 41% 3*
3 Draws: 70% 3*
1 Draw: 5% x10 20% x5 25% x3 50% x2
1 Draw: 0.1% 5*
1 Draw: 0.2% 4*
2 Draws: 6% 4* 8% 3* 35% 2* 51% 1*
1 Draw: 6% 4* 8% 3* 35% 2* 51% 1*
1-5%
1 Draw: 1% 4* 99% 3*
2 Draws: 6% EHT 10% ETT 84% Gray
1 Draw: 100% x50
Reset: 1 Draw: 5% x1
1 Draw: 15% 5*
2 Draws: 45% 4*
3 Draws: 65% 3*
1 Draw 10% x10 30% 5x 30% x3 30% x2
1 Draw: 0.5% 5*
1 Draw: 1% 4*
2 Draws: 8% 4* 10% 3* 35% 2* 47% 1*
2 Draws: 8% 4* 10% 3* 37% 2* 45% 1*
Top 1%
1 Draw: 2% 4* 98% 3*
3 Draws: 10% EHT 40% ETT 50% Gray
1 Draw: 25% x100 75% x50
Reset: 1 Draw: 30% x1
1 Draw: 20% 5*
2 Draws: 60% 3*
3 Draws: 87% 3*
1 Draw: 25% x10 35% x5 40% x3
1 Draw: 1% 5* 2% 4*
2 Draws: 14% 4* 20% 3* 36% 2* 30% 1*
3 Draws: 14% 4* 20% 3* 30% 2* 36% 1*
As of the 13th Raid Tournament, it was announced that further updates to the loot were not planned:
It has been observed that approximately 1.5 million players sign up for these tournaments as of May 2020. Using this approximation, some key break points for rewards are:
Tier
Low Rank
Top 1%
15,000
1-5%
75,000
5-10%
150,000
10-25%
375,000
25-50%
750,000
50-75%
1,125,000
75-100%
Just Sign Up
Remember that these are approximations assuming 1.5 million players sign up. The actual rank needed for a certain tier could be higher or lower on any given tournament. The required score will also vary depending on the players’ performance and the Tournament rules.
Bug Reporting
Please see these threads for existing bug reports before creating a new report
I am wondering why we have 32 different tournaments only. With 3 rules x 3 rarity restrictions x 6 colour restrictions, 54 different tournament formats would be possible.
Which is why 5* tournaments are off limits for non-donaters. After 2 years in the game you have around 10 leveled 5* heroes, usually disproportionally of one color (3 green, not a single red) so there’s only couple workable teams, even when you select 4* to match against opponent’s center.
What’s the point at all, if with 4100 max rainbow team I have to always play with 3700 ones against 4300-4700 in 9 out of 10 cases?!
Which is why as non-donaters I purposely witholding emblems for 5*, I give them to 4* instead so their power at +20 are similiar to non-emblemed 5*. Now I have 28 heroes whose power is between 735-795. 12Ă— 5* + 16Ă— 4*.
That way my attack team is not too far below the best 5.
Log of Raid Tournament Special Rules and Restrictions
Overview of Weekly Raid Tournaments
Tournament
Attacking
Matchmaking
Scoring
Defense Team Grade
Restrictions
Special Rules
Rewards
Bug Reporting
Related Links
Typical tho…
Well, there’s TRWTF 
right there… even for a Gill-Ra only event, never train Gill-Ra! 
