Cast the instant or sorcery spell from your hand by paying its mana cost.
Holding priority, cast Increasing Vengeance from your graveyard for its flashback cost by paying {3}{R}{R}, targeting the instant or sorcery.
Increasing Vengeance's demonstrate ability triggers, causing you and an opponent to copy Increasing Vengeance, with your copy targeting the original Increasing Vengeance.
The Twelfth Doctor triggers, putting a +1/+1 counter on it.
Resolve the copy of Increasing Vengeance, copying Increasing Vengeance, with the copy targeting the original Increasing Vengeance.
Repeat from step 4.

Infinite magecraft triggers

Infinite +1/+1 counters on a creature

The Twelfth Doctor

Increasing Vengeance

Cast Glorious End from your graveyard by paying {2}{R}, causing it to gain demonstrate due to The Twelfth Doctor.
Glorious End's demonstrate ability triggers, causing you and an opponent to copy it.
Resolve the opponent's copy of Glorious End, ending the turn, thus exiling all other spells and abilities on the stack.
The opponent will then lose the game during their next end step due to Glorious End's triggered ability.

Target opponent loses the game at the beginning of their next end step

Kess, Dissident Mage

Glorious End

Cast Charismatic Conqueror from your graveyard by paying {1}{W}
Charismatic Conqueror's demonstrate ability triggers, causing you and an opponent to copy it.
Resolve the opponent's copy of Charismatic Conqueror, and then resolve your copy of Charismatic Conqueror.
When your Charismatic Conqueror token enters the battlefield,  the opponent's Charismatic Conqueror triggers, causing you to tap your Charismatic Conqueror token.
Resolve the original Charismatic Conqueror spell.
When the nontoken Charismatic Conqueror enters the battlefield, the opponent's Charismatic Conqueror triggers, causing you to not tap the nontoken Charismatic Conqueror, and causing the opponent to create a 1/1 Vampire creature token.
When the opponent's Vampire token enters the battlefield, both Charismatic Conquerors you control trigger, causing you to create at least one 1/1 Vampire creature token.
When your Vampire token enters the battlefield, the opponent's Charismatic Conqueror triggers, causing you to not tap the Vampire token, and causing the opponent to create a 1/1 Vampire creature token.
Repeat from step 7.

Infinite ETB

Infinite creature tokens

Infinite ETB for target opponent

Infinite creature tokens for target opponent

Charismatic Conqueror

Serra Paragon

Cast Charismatic Conqueror from the top of your library by paying {1}{W}.
Charismatic Conqueror's demonstrate ability triggers, causing you and an opponent to copy it.
Resolve the opponent's copy of Charismatic Conqueror, and then resolve your copy of Charismatic Conqueror.
When your Charismatic Conqueror token enters the battlefield,  the opponent's Charismatic Conqueror triggers, causing you to tap your Charismatic Conqueror token.
Resolve the original Charismatic Conqueror spell.
When the nontoken Charismatic Conqueror enters the battlefield, the opponent's Charismatic Conqueror triggers, causing you to not tap the nontoken Charismatic Conqueror, and causing the opponent to create a 1/1 Vampire creature token.
When the opponent's Vampire token enters the battlefield, both Charismatic Conquerors you control trigger, causing you to create at least one 1/1 Vampire creature token.
When your Vampire token enters the battlefield, the opponent's Charismatic Conqueror triggers, causing you to not tap the Vampire token, and causing the opponent to create a 1/1 Vampire creature token.
Repeat from step 7.

Fortune Teller's Talent

Cast Appa by paying its mana cost.
When Appa enters, it triggers, exiling Charismatic Conqueror.
Cast Charismatic Conqueror from exile by paying {2}.
Charismatic Conqueror's demonstrate ability triggers, causing you and an opponent to copy it.
Resolve the opponent's copy of Charismatic Conqueror, and then resolve your copy of Charismatic Conqueror.
When your Charismatic Conqueror token enters the battlefield,  the opponent's Charismatic Conqueror triggers, causing you to tap your Charismatic Conqueror token.
Resolve the original Charismatic Conqueror spell.
When the nontoken Charismatic Conqueror enters the battlefield, the opponent's Charismatic Conqueror triggers, causing you to not tap the nontoken Charismatic Conqueror, and causing the opponent to create a 1/1 Vampire creature token.
When the opponent's Vampire token enters the battlefield, both Charismatic Conquerors you control trigger, causing you to create at least one 1/1 Vampire creature token.
When your Vampire token enters the battlefield, the opponent's Charismatic Conqueror triggers, causing you to not tap the Vampire token, and causing the opponent to create a 1/1 Vampire creature token.
Repeat from step 9.

Combos with "The Twelfth Doctor"