Coagulated entity

Card text:Choose X other ready Blood Brothers you control who belong to the same circle as this acting vampire.
[san] Enter combat with a ready minion controlled by another Methuselah. This acting vampire has +X strength and +X capacity. Before the combat begins, each chosen vampire must move 1 blood to the acting vampire or this action is canceled.
[SAN] As [san] above, and this vampire may prevent up to X damage this combat.

Just to be sure I understand this card correctly.
If a minion playing this card succesfully enters combat with a chosen target minion, with [san] both capacity and strength increases by X, permanently. (since in the sentence there is no reference to "this" or "that" combat)
And if blocked non of the +X effects apply.

Side question: in rush action cards a special effect, like optional maneuver, applies in "this combat" (for example in bums rush) or "that combat" (nose of the hound). Do they both refer to a combat from succesful, non-blocked action in a similar way?

Lasu wrote:

If a minion playing this card succesfully enters combat with a chosen target minion, with [san] both capacity and strength increases by X, permanently. (since in the sentence there is no reference to "this" or "that" combat)

It's not permanent, no. It's restricted to "this acting vampire". When the action's over, it's no longer "this acting vampire".

Lasu wrote:

And if blocked non of the +X effects apply.

If blocked, none of the effects of the action apply - including the +X, or the enter combat etc.

Lasu wrote:

Side question: in rush action cards a special effect, like optional maneuver, applies in "this combat" (for example in bums rush) or "that combat" (nose of the hound). Do they both refer to a combat from succesful, non-blocked action in a similar way?

The effects of all actions only occur if they're successful (barring particular card text, like Force of Will). The optional manuever from Bum's Rush only occurs if the action is successful. The referendum from Kine Resources Contested only occurs if the action is successful.