okay, pretty confusing, but i think this one would do the job.
Selective Hatred UUB
Instant
Choose two colors. Counter target spell with two mana symbols of each color in its mana cost. Its controller loses 3 life.
Vengeance of the Weak 1UUB
Instant
Until end of turn, whenever a counter is removed from a permanent you control, target player loses life equal to that permanent's converted mana cost then draw a card.
Sigil Mourning 3GW
Enchantment
Whenever you discard a multicolored card, you may pay 2. If you do, put X +1/+1 counter on each creature you control where X is that card's converted mana cost.
Radiation Pulse 2BG
Enchantment
When ~ comes into play, you may search your library for a multicolored instant card, reveal it, and put it into your hand. If you do, Shuffle your library.
Whenever a two or more creatures of the same name are destroyed in a turn, target player loses X life where X is twice the number of creatures destroyed this way.
Eternal Synthesis 3W
Enchantment
Whenever an opponent gains control of a card you control, you gain life equal to its converted mana cost.
Whenever a card is cycled, put +1/+1 counters on each creature you control equal to the number of that card's colors.
3WU
Enchantment
Whenever a card would be put into an opponent's hand from anywhere, remove it from the game instead. you gain 1 life.
Selective Hatred
UUB
Instant
Choose two colors. Counter target spell with two mana symbols of each color in its mana cost. Its controller loses 3 life.
2B
Creature - Demon
When ~ comes into play, target creature can't attack or block until end of turn.
3/3
1UUB
Instant
Until end of turn, whenever a counter is removed from a permanent you control, target player loses life equal to that permanent's converted mana cost then draw a card.
3GW
Enchantment
Whenever you discard a multicolored card, you may pay 2. If you do, put X +1/+1 counter on each creature you control where X is that card's converted mana cost.
2BG
Enchantment
When ~ comes into play, you may search your library for a multicolored instant card, reveal it, and put it into your hand. If you do, Shuffle your library.
Whenever a two or more creatures of the same name are destroyed in a turn, target player loses X life where X is twice the number of creatures destroyed this way.
5BBBSorcery
Destroy all permanents each opponent controls.
2BB
Enchantment
Whenever you skip your draw step, target player loses 5 life.
3W
Enchantment
Whenever an opponent gains control of a card you control, you gain life equal to its converted mana cost.
Whenever a card is cycled, put +1/+1 counters on each creature you control equal to the number of that card's colors.
2UB
Enchantment
Whenever a permanent makes you pay 1, target player loses 2 life.
i dunno if the wording checks out, but you get the point.
Primitive Consequence
3BB
Instant
Target player loses life equal to the number of nonland, nonartifact permanents he or she controls.
Lack of Etherium
2WB
Instant
Until end of turn, whenever an artifact comes into play, remove it from the game.
Electromagnetic Pulse
2WB
Instant
Destroy all permanents with converted mana cost 2 or less.
You gain 1 life for every permanent destroyed this way.
2WB
Enchantment
Whenever a creature you control is removed from the game, each opponent loses life equal to its power.
3WU
Enchantment
Creatures you control have shroud.
You have shroud as long as you control 2 or more creatures.