Amumu’s default build works because he rarely wins fights through a single burst window; he wins them by locking down space, maintaining contact, and punishing enemies who remain grouped around him.
Shimmering Spark
AoE damage around him, perfect synergy with W Despair
Carry buff after engaging with R Curse of the Sad Mummy
reflected AA damage, Amumu reste collé with W in melee
Plated Steelcaps
Active after Q or R, gives him resistance massive at the moment of his engage.
Magic shield useful against AP-heavy comps that want to the punir during the engage.
Reduces incoming damage during the CC phase that follows the Q bandage.
Scales tank with his clears jungle repeated, making him more durable.
Q (Bandage Toss) is a dash that triggers penetration on impact.