Kusari-Gama [Champions of Kamigawa] Darkness[×2] The creature enters the battlefield

The creature enters the battlefield with five times that many +1/+1 counters on it

Set: Sword & Shield: Vivid Voltage Type: Fire Rarity: Uncommon Retreat cost: Colorless

Caller of Wirewood

Set: 30th Anniversary Edition Type: Instant Rarity: Rare Cost: {U} Change the text of target spell or permanent by replacing all instances of one basic land type with another

how could I know they'd explode

Kusari-Gama [Champions of Kamigawa] Darkness[×2] The creature enters the battlefieldSet: Champions of Kamigawa Type: Artifact Equipment Rarity: Rare Cost: {3} Equipped creature has "{2}: This creature gets +1 +0 until end of turn." Whenever equipped creature deals damage to a blocking creature, Kusari Gama deals that much damage to each other creature defending player controls. Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)