What is a Combo card?

Like Command the Sandstrorm...

from the current tournament rules:

2.14.2.2 Combo
Combo: (X) - In order to play the Combo ability written in the card text box, you must have cards with the required traits (noted in the parentheses) in the card pool immediately preceding this card in the listed order. Any references given to zones in the requirements refer to attack zones. 2.14.2.2.1 The Combo keyword is a continous ability.

if your card pool has:

then you play:

since the card before it in the card pool is a low attack then you can play the combo enhance on Alaraph Achernar

if you then procede to play:

having a low attack and then a mid attack and then this attack you will have played one of algol's intended combos fully and can play the combo E on Alshain najm

Aaaaaaaaaaand stamp for ziepnir