Plague Sliver — ruling 1

Abilities that Slivers grant, as well as power/toughness boosts, are cumulative. However, for some abilities, like flying, having more than one instance of the ability doesn’t provide any additional benefit.

Plague Sliver — ruling 2

If the creature type of a Sliver changes so it’s no longer a Sliver, it will no longer be affected by its own ability. Its ability will continue to affect other Sliver creatures.

Plague Sliver — ruling 3

Each Sliver deals damage to its controller (not to Plague Sliver’s controller).

Plague Sliver : règles, fonctionnement et interactions (MTG)

Plague Sliver is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

All Slivers have "At the beginning of your upkeep, this permanent deals 1 damage to you."

How it works : Plague Sliver

Original English text — Wizards of the Coast / Scryfall

#1July 1, 2013· Wizards of the Coast
Abilities that Slivers grant, as well as power/toughness boosts, are cumulative. However, for some abilities, like flying, having more than one instance of the ability doesn’t provide any additional benefit.
No other card is named in this ruling.
#2July 1, 2013· Wizards of the Coast
If the creature type of a Sliver changes so it’s no longer a Sliver, it will no longer be affected by its own ability. Its ability will continue to affect other Sliver creatures.
No other card is named in this ruling.
#3September 25, 2006· Wizards of the Coast
Each Sliver deals damage to its controller (not to Plague Sliver’s controller).
No other card is named in this ruling.