Soltari Lancer — ruling 1

Once a creature has been blocked, that creature remains blocked and will deal and be dealt combat damage even if it gains or loses shadow or if the blocking creature gains or loses shadow.

Soltari Lancer — ruling 2

If an attacking creature has multiple evasion abilities, such as shadow and flying, a creature can block it only if that creature satisfies all of the appropriate evasion abilities.

Soltari Lancer — ruling 3

Multiple instances of shadow on the same creature are redundant.

Soltari Lancer — ruling 4

For a time, the ability that granted it first strike was a triggered ability. It has been restored to a static ability that applies continuously while the Lancer is attacking. There is never a time when the Lancer is attacking but doesn't have first strike.

Soltari Lancer : règles, fonctionnement et interactions (MTG)

Soltari Lancer 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

Shadow (This creature can block or be blocked by only creatures with shadow.) This creature has first strike as long as it's attacking.

How it works : Soltari Lancer

Original English text — Wizards of the Coast / Scryfall

#1March 19, 2021· Wizards of the Coast
Once a creature has been blocked, that creature remains blocked and will deal and be dealt combat damage even if it gains or loses shadow or if the blocking creature gains or loses shadow.
No other card is named in this ruling.
#2March 19, 2021· Wizards of the Coast
If an attacking creature has multiple evasion abilities, such as shadow and flying, a creature can block it only if that creature satisfies all of the appropriate evasion abilities.
No other card is named in this ruling.
#3March 19, 2021· Wizards of the Coast
Multiple instances of shadow on the same creature are redundant.
No other card is named in this ruling.
#4April 1, 2008· Wizards of the Coast
For a time, the ability that granted it first strike was a triggered ability. It has been restored to a static ability that applies continuously while the Lancer is attacking. There is never a time when the Lancer is attacking but doesn't have first strike.
No other card is named in this ruling.