Constellar Ptolemy M7 is a very powerful card to use in any deck, especially a constellar deck. Constellar's are a very powerful light monster xyz archetype that is lacking support cards. If more constellar support cards are released I can see them becoming a top deck in the metagame. M7 is the strongest of the xyz monsters in my opinion because of his ability to Chaos Xyz Evolution summon and to return monsters to the hand.
You can start by Xyz summoning a constellar monster then use its effect, and then summon M7 afterwards to increase the attack on the field and be able to use M7 next turn. Aside from having the very high 2700 attack, M7 can return any monster on the field or in the graveyard to its owner's hand. Which allows you to return a pesky or powerful card your opponent controls. Or you can add a constellar from your grave to your hand for an instant +1.
Combos with other cards:
M7 combo's well with Constellar Star chart. you can activate the star chart, xyz summon a monster, then if you dont see yourself xyz summoning another constellar easy the next turn wait and summon M7 that turn for an additional draw.
One of my favorite combinations is to use star chart and summon constellar pleiades. then use his effect to return star chart to hand, re activate it, then summon M7 on pleiades. for a big +2. (on your next turn you can detach pleiades, use xyz reborn on him and repeat the process - and if you xyz reborn that pleiades you can also use xyz gift for even more additinal draws)
Another combination is to summon Constellar Praesepe and activate limiter removal during the damage step for an attack of 6800. then in mainphase 2 Chaos Xyz Summon M7 using Praesepe to avoid losing the field control with limiter removal's effect in the endphase.
Ways to counteract it:
this card is very weak to spells, traps and stronger monsters. constellars have very little support cards and most rely heavily on royal decree and any form of card effect protection.
this card finds itself weak to skill drain, thunderking rai oh, the "ally of justice" archetype. and the trap card "rebound."
Easy to summon, good +1 card.
Cannot protect itself and is normally the strongest card in a constellar deck, with a mere 2700 ATK.
9/10 when used correctly, seeing as he is the most powerful card in a great deck built in the metagame.