Suitable artifact replacement power

[Invader]

I'm replacing the 1/week summon nightcrawler power from the artifact I mentioned here http://www.giantitp.com/forums/showthread.php?359629-UMD-Artifact-question to something more suitable to our current level (7th). Anyone have any good suggestions for a 1/week summoned creature for a moderately optimized game?

[Blackhawk748]

Im not sure what CR a night crawler is but you could use a Shadow Elemental of similar CR

[Invader]

Pretty ridiculous for our level lol

http://www.d20srd.org/srd/monsters/nightshade.htm

[Invader]

Im not sure what CR a night crawler is but you could use a Shadow Elemental of similar CR

Where's shadow elemental from?

[Blackhawk748]

oooook lol so how about a Huge Shadow Elemental or a Greater Shadow Elemental (Cr 9 and 11 respectively?) I figure it should be better than the party as its only once a week.

Edit: Tome of Magic