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.

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.

Multiple instances of shadow on the same creature are redundant.

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.